refactor(tui): prompt deep-module PR 3 — canonical completion + async workspace index (#220)

* refactor(tui): unify prompt completion context

* feat(tui): index workspace mentions asynchronously

* ci(typos): allow @Caf completion-prefix test token

* fix(tui): address review findings on prompt completion

- Escape now dismisses the slash-argument menu (cancel_completion fallback)
  instead of doing nothing when there is no draft command to strip.
- Strip trailing prose punctuation from unquoted @-mention highlight spans.
- Rank scoped @dir/name completions by the fragment's basename so prefix
  priority applies to path-scoped fragments.
- Drain git stdout/stderr concurrently to avoid a pipe deadlock on verbose
  output.
- Guard the mid-session HostPath.cwd() lookup so a removed working directory
  no longer crashes the prompt turn.
- Collapse a dead SLASH_ARGUMENT branch in the completion parser.
- De-duplicate the PromptLifecycle test double, make the degraded-state test
  helper multi-key-safe, and re-frame the backslash-whitespace parser test to
  document the real (non-escape-aware) contract.

* fix(tui): cancel sibling stream reader when a git reader fails

The concurrent stdout/stderr drain in _run_git used asyncio.gather, which
leaves the sibling _read_bounded coroutine running after the first reader
raises — only the process was killed, so the other reader could keep draining
a closing pipe. Move the concurrent read into _read_streams, which uses
explicit tasks and cancels+awaits both readers on any failure (or cancellation)
before propagating. Adds a regression test for a reader-exception path.

Author: elkaix

CHANGELOG.md

@@ -16,6 +16,9 @@ GitHub Releases page; `0.8.0` is the new starting line.
 ## Unreleased
 
 - Freeze the public shell prompt compatibility contract with constructor and rendering coverage.
+- Unify slash and file-mention completion behind one canonical completion context, adding quoted `@"path with spaces"` file mentions.
+- Index workspace file mentions asynchronously with a cwd-aware, generation-owned snapshot index so completion never blocks on disk or Git scans.
+- Harden prompt completion: Escape now dismisses the slash-argument menu (not just draft commands), file-mention highlighting no longer swallows trailing prose punctuation, scoped `@dir/name` completions rank basename-prefix matches first, workspace Git scans drain stdout/stderr concurrently to avoid a pipe deadlock, and a mid-session working-directory removal no longer crashes the prompt turn.
 - Keep the interactive prompt scene within the terminal height with a priority-ordered row allocator, and shut prompt background tasks/processes down with an awaited lifecycle.
 - Add xAI Grok OAuth login (browser loopback and device-code).
 - Add GitHub Copilot device-code OAuth login for individual github.com accounts.

pyproject.toml

@@ -194,6 +194,8 @@ iterm = "iterm"
 informations = "informations"
 # Project/domain-specific names and generated IDs.
 reviewr = "reviewr"
+# ASCII prefix used in a file-completion test (@caf -> "café.md").
+caf = "caf"
 fnd = "fnd"
 edn = "edn"
 Encrypter = "Encrypter"