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/web/routes/session-routes.ts

@@ -760,7 +760,7 @@ async function injectAgentSkill(casePath: string): Promise<void> {
  * dead-pane-respawn path in session.ts does, so even the FIRST relaunch of a
  * resumed conversation is pinned rather than guessed.
  */
-function resolveOmpConfigForCreate(
+export function resolveOmpConfigForCreate(
   mode: SessionMode,
   workingDir: string,
   ompConfig: OmpConfig | undefined
@@ -770,6 +770,11 @@ function resolveOmpConfigForCreate(
     return ompConfig;
   }
   const resolvedId = findLatestOmpSessionId(workingDir);
+  if (!resolvedId) {
+    console.warn(
+      `[Session] OMP: no session file found under ${workingDir} to pin --resume; falling back to ambiguous --continue`
+    );
+  }
   return resolvedId ? { ...ompConfig, resumeSessionId: resolvedId } : ompConfig;
 }