feat(agent-cases): tag agent-spawned case dirs and sweep their leftovers

A long orchestration creates one case directory per worker and deleting the
sessions never removed them, so ~/codeman-cases accumulated scratch folders
that were indistinguishable from real projects. They are now labelled and
have a cleanup path.

- src/agent-case-marker.ts: a case dir quick-start CREATES for an agent-driven
  spawn gets a .codeman-agent-case.json marker (when, by whom, parent session,
  mode). Only the create branch writes it, so a linked case, a cloned repo or
  any pre-existing path is never labelled; reading is total, so a malformed
  marker means "not agent-created" rather than a half-trusted entry.
- The signal is the new X-Codeman-Agent-Origin header the skill preamble sets
  on its shared curl (preamble bumped to 1.22.0), or an agentOrigin body
  field, falling back to a resolved parentSessionId so a worker spawned by a
  stale skill copy is still labelled.
- GET /api/cases publishes it as agentCreated; GET /api/cases/agent-created is
  a read-only cleanup listing adding inUse and modifiedAt; Add Case -> Manage
  badges each case and offers a review-then-delete sweep that names every
  directory in its confirm and skips any case a live session is working in.
  Removal stays on the existing DELETE /api/cases/:name.
- Agent preamble caches are collected too: ~/.cache/codeman-agent-<id>.sh was
  written per claude session and never removed (236 leftovers measured on a
  working machine). Now deleted with the session and swept at boot, guarded by
  a live-session keep set plus a 7-day age floor.

Verified end to end on an isolated instance: marker written for header, body
and lineage-only spawns, absent with no agent signal and for a pre-existing
directory; inUse flipping on session end; badge, sticky bar, confirm and sweep
driven in a browser; preamble seeded on create, removed on delete, boot sweep
taking only the aged orphans.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/agent-case-marker.ts

@@ -0,0 +1,183 @@
+/**
+ * @fileoverview The marker file that records a case directory as one Codeman scaffolded
+ * FOR an agent-spawned session, so scratch worker workspaces can be told apart from the
+ * user's real projects long after the sessions that created them are gone.
+ *
+ * Why a file in the case directory rather than a central registry in `~/.codeman`:
+ * the thing being labelled is a directory on the user's disk, and the label has to
+ * survive everything that can happen to Codeman's own state (a wiped data dir, a
+ * different instance, a hand-moved case). A registry would also need stale-entry
+ * pruning and owner scoping of its own, while a marker is deleted by the same `rm -rf`
+ * that deletes the case, and is discoverable by a user who just runs `ls -a`.
+ *
+ * ⚠️ Written ONLY on the path that CREATES the directory (`POST /api/quick-start`'s
+ * `!existsSync` branch). A linked case, a cloned repo, a git worktree or any other
+ * pre-existing directory must never be labelled agent-created: the label drives a
+ * cleanup affordance, and mislabelling someone's repo there is the one failure mode
+ * that costs real work. `POST /api/sessions` takes an existing `workingDir` and so
+ * writes no marker at all, by construction.
+ *
+ * ⚠️ Reading is strict and total: anything that does not parse as a version-1 marker
+ * (truncated write, hand-edited junk, a user's unrelated file of the same name) reads
+ * as "not agent-created" rather than as a partially-trusted entry. A marker is
+ * metadata; deleting the file is the supported way to adopt a scratch case as a real
+ * one, which is what the `note` field written into it tells the user.
+ */
+
+import { readFile, writeFile } from 'node:fs/promises';
+import { join } from 'node:path';
+
+/** Marker filename inside the case directory. Dot-prefixed so it stays out of the way. */
+export const AGENT_CASE_MARKER_FILE = '.codeman-agent-case.json';
+
+/** Current marker schema version. A marker of any other version reads as absent. */
+export const AGENT_CASE_MARKER_VERSION = 1;
+
+/**
+ * Origin recorded when a create request carried a resolvable spawning session but no
+ * explicit origin of its own (an agent driving the API by hand, or an older copy of
+ * the skill). Nothing in the browser UI sets lineage, so this really does mean "another
+ * session spawned this", not "a human clicked Run".
+ */
+export const AGENT_ORIGIN_SPAWNED_BY_SESSION = 'agent-session';
+
+/** Origin the packaged agent skill sends on its shared curl invocation. */
+export const AGENT_ORIGIN_CODEMAN_SKILL = 'codeman-skill';
+
+/** Longest accepted origin token (the value is echoed into the UI and the marker). */
+const MAX_ORIGIN_LENGTH = 32;
+
+/** Longest accepted free-text field read back out of a marker. */
+const MAX_MARKER_FIELD_LENGTH = 200;
+
+/** Lowercase token: what an origin may look like on the wire and on disk. */
+const AGENT_ORIGIN_PATTERN = /^[a-z0-9][a-z0-9._-]*$/;
+
+/** Explains the file to whoever finds it in their case directory. */
+const MARKER_NOTE =
+  'Created by a Codeman agent worker (see the Manage tab in Add Case). ' +
+  'Delete this file to keep the case out of the agent-case cleanup list; ' +
+  'deleting the whole directory removes the case.';
+
+/**
+ * What a case directory records about the agent spawn that created it.
+ * Every field beyond `version`/`createdAt`/`createdBy` is decoration for the cleanup UI.
+ */
+export interface AgentCaseMarker {
+  version: typeof AGENT_CASE_MARKER_VERSION;
+  /** ISO timestamp of the spawn that created the directory. */
+  createdAt: string;
+  /** Who asked: `codeman-skill`, `agent-session`, or another caller's own token. */
+  createdBy: string;
+  /** Full id of the session that spawned the worker, when one resolved. */
+  parentSessionId?: string;
+  /** That session's display name at spawn time, so the user recognises it later. */
+  parentSessionName?: string;
+  /** Run mode the worker was started in (`claude`, `deepseek`, …). */
+  mode?: string;
+  /** Owner the case was created for, in multi-user mode. */
+  owner?: string;
+}
+
+/**
+ * Validate an origin token coming off the wire (`agentOrigin` body field or the
+ * `X-Codeman-Agent-Origin` header). Returns `undefined` for anything that is not a
+ * short lowercase token — the value reaches the UI and a JSON file, so it is
+ * allowlisted rather than escaped at each use.
+ */
+export function normalizeAgentOrigin(raw: unknown): string | undefined {
+  if (typeof raw !== 'string') return undefined;
+  const value = raw.trim().toLowerCase();
+  if (!value || value.length > MAX_ORIGIN_LENGTH) return undefined;
+  return AGENT_ORIGIN_PATTERN.test(value) ? value : undefined;
+}
+
+/** Trim an optional free-text marker field to something safe to store and render. */
+function normalizeField(raw: unknown): string | undefined {
+  if (typeof raw !== 'string') return undefined;
+  const value = raw.trim();
+  return value ? value.slice(0, MAX_MARKER_FIELD_LENGTH) : undefined;
+}
+
+/**
+ * Build a marker from a spawn's details. Pure, so the route can hand it straight to
+ * the writer and the tests can assert on the shape without touching a disk.
+ */
+export function buildAgentCaseMarker(input: {
+  createdBy: string;
+  createdAt?: Date;
+  parentSessionId?: string;
+  parentSessionName?: string;
+  mode?: string;
+  owner?: string;
+}): AgentCaseMarker {
+  const marker: AgentCaseMarker = {
+    version: AGENT_CASE_MARKER_VERSION,
+    createdAt: (input.createdAt ?? new Date()).toISOString(),
+    createdBy: normalizeAgentOrigin(input.createdBy) ?? AGENT_ORIGIN_SPAWNED_BY_SESSION,
+  };
+  const parentSessionId = normalizeField(input.parentSessionId);
+  const parentSessionName = normalizeField(input.parentSessionName);
+  const mode = normalizeField(input.mode);
+  const owner = normalizeField(input.owner);
+  if (parentSessionId) marker.parentSessionId = parentSessionId;
+  if (parentSessionName) marker.parentSessionName = parentSessionName;
+  if (mode) marker.mode = mode;
+  if (owner) marker.owner = owner;
+  return marker;
+}
+
+/**
+ * Parse marker JSON. Returns `null` for anything that is not a well-formed version-1
+ * marker, including a valid-JSON object of the wrong shape — see the strictness note
+ * in the file header.
+ */
+export function parseAgentCaseMarker(raw: string): AgentCaseMarker | null {
+  let value: unknown;
+  try {
+    value = JSON.parse(raw);
+  } catch {
+    return null;
+  }
+  if (!value || typeof value !== 'object' || Array.isArray(value)) return null;
+
+  const record = value as Record<string, unknown>;
+  if (record.version !== AGENT_CASE_MARKER_VERSION) return null;
+
+  const createdAt = normalizeField(record.createdAt);
+  const createdBy = normalizeAgentOrigin(record.createdBy);
+  if (!createdAt || !createdBy || Number.isNaN(Date.parse(createdAt))) return null;
+
+  return buildAgentCaseMarker({
+    createdBy,
+    createdAt: new Date(createdAt),
+    parentSessionId: normalizeField(record.parentSessionId),
+    parentSessionName: normalizeField(record.parentSessionName),
+    mode: normalizeField(record.mode),
+    owner: normalizeField(record.owner),
+  });
+}
+
+/**
+ * Write the marker into `casePath`. Best-effort by design: the marker is metadata for
+ * a later cleanup, and a failed write must never fail the worker spawn that is the
+ * point of the request. Returns whether it landed.
+ */
+export async function writeAgentCaseMarker(casePath: string, marker: AgentCaseMarker): Promise<boolean> {
+  try {
+    const body = JSON.stringify({ ...marker, note: MARKER_NOTE }, null, 2);
+    await writeFile(join(casePath, AGENT_CASE_MARKER_FILE), `${body}\n`, 'utf-8');
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+/** Read the marker out of `casePath`, or `null` if there isn't a valid one. */
+export async function readAgentCaseMarker(casePath: string): Promise<AgentCaseMarker | null> {
+  try {
+    return parseAgentCaseMarker(await readFile(join(casePath, AGENT_CASE_MARKER_FILE), 'utf-8'));
+  } catch {
+    return null;
+  }
+}