fix(review): harden Codex generated-artifact attachment pipeline (PR #150)

- Pass the attachment request `source` through the server deps lambda and make
  it a required param on SessionListenerDeps.registerAttachment + the wiring
  event type (the 2-arg lambda silently dropped `source`, force-confining every
  codex-generated artifact — the feature never worked outside the workspace);
  new test/session-listener-wiring.test.ts asserts the pass-through
- Gate the Codex `Saved to: file://` scanner on mode === 'codex' via a
  codexArtifacts option threaded from the session call site; magic links stay
  mode-agnostic; tests assert claude/shell sessions never emit codex-generated
  requests
- Decide the generated-artifact trust policy on the realpath-RESOLVED path
  (unresolvable → force-confined) and anchor the ~/.codex marker dirs to
  os.homedir() prefixes with startsWith instead of substring matching; symlink
  escape + unanchored-marker regression tests added
- Run the Codex scanner on stripAnsi'd data so trailing SGR sequences don't
  ride into the captured URL; styled 'Saved to:' test added
- Extend generateFirstPageThumbnail with jpg/jpeg/gif/webp passthrough and
  per-extension content types (mirrors the png passthrough) so the PR's new
  image formats render real thumbnails instead of 204 letter-tiles

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

src/session.ts

@@ -1231,9 +1231,11 @@ export class Session extends EventEmitter {
     }
 
     // Scan terminal output for attachment requests. `codeman://attach?...` is an
-    // explicit magic link; Codex generated images report `Saved to: file://...`.
-    // The web server applies the trust boundary for each request source.
-    const attachmentRequests = parseTerminalAttachmentRequests(data);
+    // explicit magic link (all modes); Codex generated images report
+    // `Saved to: file://...` — that scanner (and its relaxed trust policy) is
+    // only enabled for codex-mode sessions. The web server applies the trust
+    // boundary for each request source.
+    const attachmentRequests = parseTerminalAttachmentRequests(data, { codexArtifacts: this.mode === 'codex' });
     for (const request of attachmentRequests) {
       const seenKey = `${request.source}:${request.path}`;
       if (this._attachmentMagicSeen.has(seenKey)) continue;