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>

src/omp-transcript.ts

@@ -100,7 +100,10 @@ function parseOmpSessionFile(filePath: string): OmpHistorySession | null {
     }
     if (!entry || typeof entry !== 'object') continue;
     const e = entry as Record<string, unknown>;
-    if (e.type === 'session' && typeof e.id === 'string' && typeof e.cwd === 'string') {
+    if (e.type === 'session' && typeof e.id === 'string' && typeof e.cwd === 'string' && e.cwd.startsWith('/')) {
+      // A corrupted or malformed session file could carry a relative or empty
+      // cwd; requiring an absolute path keeps a downstream resume attempt
+      // from being pointed at a nonsense working directory.
       sessionId = e.id;
       workingDir = e.cwd;
     } else if (e.type === 'message') {