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/web/server.ts

@@ -1330,7 +1330,8 @@ export class WebServer extends EventEmitter {
         }
       },
       getStore: () => this.store,
-      registerAttachment: (id: string, filePath: string) => this.registerAttachment(id, filePath),
+      registerAttachment: (id: string, filePath: string, source: 'external' | 'codex-generated') =>
+        this.registerAttachment(id, filePath, source),
     };
   }
 
@@ -1343,13 +1344,17 @@ export class WebServer extends EventEmitter {
    * session workspace — passive magic links can't expose arbitrary host files.
    * Deliberate cross-workspace attachment goes through the explicit,
    * Origin-guarded `POST /attachments` route (and `codeman attach`, which POSTs
-   * directly inside a managed session). Registration also enforces the COD-53
-   * blocklist as defense-in-depth.
+   * directly inside a managed session). Codex-mode `Saved to:` requests
+   * (`source: 'codex-generated'`) instead go through
+   * registerGeneratedArtifactAttachment, which stays force-confined unless the
+   * realpath-resolved target is inside the workspace or a home-anchored
+   * `~/.codex*` generated-artifact directory. Registration also enforces the
+   * COD-53 blocklist as defense-in-depth.
    */
   private async registerAttachment(
     sessionId: string,
     filePath: string,
-    source: 'external' | 'codex-generated' = 'external'
+    source: 'external' | 'codex-generated'
   ): Promise<void> {
     const session = this.sessions.get(sessionId);
     if (!session) return;