harden(omp): resume-path test coverage, silent-fallback logging, cwd validation

Follow-up from a full-branch review pass (Opus) of the omp-mode integration:

- Add pinning tests for resolveOmpConfigForCreate() (session-routes.ts),
  exported to make it testable: the exact "resume this OMP row from
  history" pipeline that mangleOmpWorkingDir's earlier bug lived in had
  zero coverage despite being the resolver module's whole reason to exist.
- Log a warning when findLatestOmpSessionId() finds nothing on disk and
  continuation silently degrades to omp's own ambiguous --continue,
  in both call sites (session create and respawn pinning) - previously
  silent, making the degradation invisible to anyone debugging it.
- Require an absolute cwd before trusting a session file's working
  directory in omp-transcript.ts's parser, so a corrupted/malformed
  session file can't point a downstream resume at a relative or empty
  path.
- Document (don't speculatively fix) an unverified symlinked-$HOME edge
  case in mangleOmpWorkingDir(): the review's suggested realpath() fix
  assumes omp itself resolves symlinks before mangling, which is
  unconfirmed - guessing wrong there would trade one silent mismatch
  for a different one.
- Incidental: fixed unrelated pre-existing prettier drift in
  session-routes.ts (antigravity/opencode dynamic import line-wrapping)
  that was blocking the pre-commit formatting gate on this file.

Confirmed as a non-issue: the model-name regex allowing "/" is
intentional (provider/model ids like "crof/glm-5.2" were used
successfully in live testing).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

test/omp-session-resolver.test.ts

@@ -21,6 +21,7 @@ import { homedir } from 'node:os';
 import { join } from 'node:path';
 import { afterEach, describe, expect, it } from 'vitest';
 import { findLatestOmpSessionId, mangleOmpWorkingDir } from '../src/utils/omp-session-resolver.js';
+import { resolveOmpConfigForCreate } from '../src/web/routes/session-routes.js';
 
 describe('mangleOmpWorkingDir', () => {
   it('strips the home prefix before dash-replacing a home-relative path', () => {
@@ -67,3 +68,61 @@ describe('findLatestOmpSessionId', () => {
     expect(findLatestOmpSessionId(join(homedir(), 'never-launched'))).toBeNull();
   });
 });
+
+describe('resolveOmpConfigForCreate', () => {
+  // The exact pipeline "resume this OMP row from the history list" drives:
+  // POST /api/sessions with mode:'omp' + ompConfig:{continueSession:true}
+  // must come back with resumeSessionId PINNED to the real omp transcript
+  // uuid, not left as the ambiguous continueSession flag alone. This was the
+  // one path flagged by review as having zero coverage despite being the
+  // exact mechanism the whole resolver module exists to serve.
+  const workingDir = join(homedir(), 'codeman-cases', 'resume-test');
+  const sessionDir = join(homedir(), '.omp', 'agent', 'sessions', '-codeman-cases-resume-test');
+
+  afterEach(() => {
+    rmSync(join(homedir(), '.omp'), { recursive: true, force: true });
+  });
+
+  it('pins resumeSessionId from disk when resuming with only continueSession set', () => {
+    mkdirSync(sessionDir, { recursive: true });
+    writeFileSync(join(sessionDir, '2026-08-27T17-31-08-001Z_real-omp-uuid.jsonl'), '{}');
+
+    const resolved = resolveOmpConfigForCreate('omp', workingDir, { continueSession: true });
+
+    expect(resolved).toEqual({ continueSession: true, resumeSessionId: 'real-omp-uuid' });
+  });
+
+  it('does not attempt resolution when resumeSessionId is already explicit', () => {
+    mkdirSync(sessionDir, { recursive: true });
+    writeFileSync(join(sessionDir, '2026-08-27T17-31-08-001Z_disk-uuid.jsonl'), '{}');
+
+    const resolved = resolveOmpConfigForCreate('omp', workingDir, {
+      continueSession: true,
+      resumeSessionId: 'already-pinned',
+    });
+
+    // Must return the caller's id unchanged, never overwrite it with whatever
+    // happens to be newest on disk.
+    expect(resolved).toEqual({ continueSession: true, resumeSessionId: 'already-pinned' });
+  });
+
+  it('leaves ompConfig unchanged when continueSession is not set', () => {
+    const resolved = resolveOmpConfigForCreate('omp', workingDir, {});
+    expect(resolved).toEqual({});
+  });
+
+  it('leaves ompConfig unchanged when nothing is on disk to resolve', () => {
+    const resolved = resolveOmpConfigForCreate('omp', join(homedir(), 'never-launched'), {
+      continueSession: true,
+    });
+    expect(resolved).toEqual({ continueSession: true });
+  });
+
+  it('returns undefined for a non-omp mode regardless of ompConfig', () => {
+    expect(resolveOmpConfigForCreate('claude', workingDir, { continueSession: true })).toBeUndefined();
+  });
+
+  it('returns undefined when ompConfig is undefined', () => {
+    expect(resolveOmpConfigForCreate('omp', workingDir, undefined)).toBeUndefined();
+  });
+});