fix(cases): bounded path probe landing fixes (#516)

- hooks-config: a probe the bulk cap refused gets ONE bounded re-probe past the
  cap (probeBeforeTouching), and whatever is still unknown is skipped. The
  per-spawn hook and statusLine helpers used to fall back to an unbounded
  lstat/readFile there, which on a dead workspace never settled and could take
  the last threadpool workers (and hang the boot hook sweep). New test: cap
  engaged, stat/lstat/readFile hanging on two more paths; both helpers return.
- describeUnknownPath()/unknownPathReason(): POST /api/sessions, quick-start and
  GET /api/cases/:name now say a folder was not checked (other mounts are still
  not answering) instead of blaming a healthy folder at the stall ceiling.
  errorCodes unchanged.
- #535 x #516: Create in a custom folder probes the parent through the bounded
  probe before realpath/stat/lstat/readdir touch it; an unknown parent is 422
  OPERATION_FAILED (UNREACHABLE) within the probe timeout. New test.
- Docs: MAX_STALLED default is 2 (follows UV_THREADPOOL_SIZE), CaseInfo
  .unreachable covers a refused probe, the boot sweep skips an unanswering
  workspace, a CLAUDE.md gotcha for bounded probes, verbs.md documents the 422
  (plugin mirror synced), api-reference documents the custom-folder 422.
- Tests: the launcher case-lookup describe is no longer nested in the Grok
  block, and the cap-below-ceiling test no longer depends on an inherited
  UV_THREADPOOL_SIZE / CODEMAN_PATH_PROBE_MAX_STALLED.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/architecture-invariants.md

@@ -321,7 +321,7 @@ So: `_confirmIdle()` (session.ts) requires the pane to go quiet, and then asks t
 
 **Hook events**: Claude Code hooks trigger via `/api/hook-event`. Key events: `permission_prompt`, `elicitation_dialog`, `elicitation_complete`, `elicitation_response`, `idle_prompt`, `stop`, `teammate_idle`, `task_completed`, `prompt_submitted` (UserPromptSubmit, #367: a Claude pane reports its live conversation id first-hand). See `src/hooks-config.ts`; upstream hook semantics mirrored in `docs/claude-code-hooks-reference.md`.
 
-⚠️ **Every claude session INSTALLS the hooks block into its workspace** (`applyWorkspaceHooks` in hooks-config.ts → `ensureCodemanHooks`, an add-only merge that keeps a user's own handlers), from EVERY claude create path — both interactive routes, cron fires, legacy scheduled runs, the plan-orchestrator one-shots — and from `restoreMuxSessions()` for sessions recovered on server start (that boot sweep skips a workspace that no longer exists, so a deleted repo with a surviving tmux session is never resurrected as an empty dir). Before 2026-08-15 hooks were written ONLY when Codeman created the case DIRECTORY, so a linked case / cloned repo — where most sessions actually run — had no hooks at all and every hook-driven surface was silently dead there: an AskUserQuestion dialog blocked the pane while the tab and the phone overview both read a calm `idle`, with no Approvals Inbox item, no push, no definitive `stop`/`idle_prompt` for respawn and no `stop`/`blocked` for the wait endpoints.
+⚠️ **Every claude session INSTALLS the hooks block into its workspace** (`applyWorkspaceHooks` in hooks-config.ts → `ensureCodemanHooks`, an add-only merge that keeps a user's own handlers), from EVERY claude create path — both interactive routes, cron fires, legacy scheduled runs, the plan-orchestrator one-shots — and from `restoreMuxSessions()` for sessions recovered on server start (that boot sweep skips a workspace that no longer exists, so a deleted repo with a surviving tmux session is never resurrected as an empty dir, and skips one that does not answer, such as a linked case on an unreachable mount, without waiting on it: `applyWorkspaceHooks` asks the bounded path probe, retries one capacity-refused probe past the bulk cap, and skips whatever is still "unknown" rather than touching it with an unbounded `lstat`). Before 2026-08-15 hooks were written ONLY when Codeman created the case DIRECTORY, so a linked case / cloned repo — where most sessions actually run — had no hooks at all and every hook-driven surface was silently dead there: an AskUserQuestion dialog blocked the pane while the tab and the phone overview both read a calm `idle`, with no Approvals Inbox item, no push, no definitive `stop`/`idle_prompt` for respawn and no `stop`/`blocked` for the wait endpoints.
 
 The escape hatch is the synced `workspaceHooksEnabled` setting (App Settings → Agents & CLIs → Claude, **default ON**); OFF restores the old behavior, where a Codeman block that is already there is still refreshed when stale (COD-91) but one is never added. ⚠️ Route the decision through `applyWorkspaceHooks` rather than calling `ensureCodemanHooks` at a new site, or the setting silently stops applying to that path.