bug(conversations): Codex prompt search matches injected AGENTS.md and environment text #1419

Found by review b of #1407. This predates #1407.

Where

• Search reads raw source.prompts() texts (service.ts:137-140).
• foldCodexRecord (promptFolder.ts:494-499) accepts every role-user response_item, including Codex's injected AGENTS.md and <environment_context> blocks.
• Only View Prompts filters. It applies unwrapUserText (service.ts:177-183); search does not.

Sequence

A Codex conversation's AGENTS.md contains token X, and no typed prompt does. Searching X lists the row as a prompt match.

Direction

Apply the same unwrapUserText filter on the search path. Add a current-shape (0.157) prompt-folder extraction assertion, which the #1363 thread also asked for.