feat(web): a prose mention of a produced file opens it

The chatFileMentions service (provided by ui-deliverables beside its
turn-tail entry, reached via ctx.get) resolves inline-code tokens in the
closing message against the turn's produced locations: exact path or
unique basename links, ambiguity and unknowns stay inert. MarkdownText
gains the optional fileMentions seam — settled renders only, never
inside anchors.

packages/client/ui-deliverables/README.md

@@ -8,6 +8,8 @@ Produced-files feature owner: registers the deliverables row a finished turn end
 
 `ProducedFiles` renders the row between the closing message's body and its IconActions footer: a quiet label, up to six chips (basename text, full path as the `title`), and an explicit remainder count past the cap. Each chip opens through the owner-supplied `openFile` — the same Host opener the tool rows use, with the chat view resolving relative paths against the session cwd. Design rationale: the [workspace file links Agent Note](../../../.agents/notes/implemented/feature/2026-07-31-web-workspace-file-links.md).
 
+The closing prose carries the same vocabulary. This plugin provides the `chatFileMentions` service the chat view consults per closing message: `producedFileMentions` resolves an inline-code token by exact path, or by being exactly the basename of exactly one produced path — a basename two paths share stays inert rather than guessing, so a mention link can never open the wrong file or 404. A resolved mention renders as the same underlined opener the row's chips are, with the full path as its `title`, and mentions never render inside anchors or streaming text. Decision record: the [inline file mentions Agent Note](../../../.agents/notes/implemented/feature/2026-08-07-web-inline-file-mentions.md).
+
 ## Model Experience
 
 None, as the row is a pure client derivation over already-logged tool metadata and nothing here reaches a model request.
@@ -18,4 +20,4 @@ None; this package neither assembles nor sends provider requests.
 
 ## Known Limitations and Deferred Work
 
-- **Prose mentions stay inert.** An inline-code file name in the closing message does not open the file yet; linking it to the same `locations` vocabulary is the stacked follow-up.
+- **Mention matching is exact path or unique basename only.** A suffix mention (`out/index.html` written as `index.html` resolves; `deep/out/index.html` written as `out/index.html` does not) stays inert; widening the matcher is deferred until a real closing-message shape needs it.