test(rebrand): residual brand-string cleanup across source and assets

A small cleanup pass to catch brand mentions that the R5 sweep missed
because they hid in:

- HTTP User-Agent format strings (`Mozilla/5.0 (compatible; deepseek-tui/`
  in `client.rs` and `fetch_url.rs`).
- Multi-line error messages whose phrase boundary straddled a line break
  ("…restart\n             deepseek-tui." in `js_execution.rs`,
  `tool_catalog.rs`, `repl/runtime.rs`).
- Doc comments mentioning `deepseek-tui` as a binary (`config/src/lib.rs`,
  `core/capacity.rs`, `tui/streaming/chunking.rs`, `features.rs`).
- Skill descriptions shipped in `crates/tui/assets/skills/*/SKILL.md`.
- Test fixtures with placeholder paths / git emails
  (`tui/external_editor.rs`, `snapshot/repo.rs`).
- `task_manager.rs`'s `cargo test -p deepseek-tui --lib` example.
- `scripts/tencent-lighthouse/doctor.sh` info-line prefix.

The remaining `deepseek-tui` mentions in the codebase are intentional
(the legacy `[[bin]]` entry in `crates/tui/Cargo.toml`, the legacy
`npm/deepseek-tui/` deprecation shim package, the CNB mirror namespace,
the security email, the legacy bin's shim source file, and historical
CHANGELOG entries) and were preserved per the rebrand anti-scope.

Local gates green: `cargo check --workspace --all-targets --locked`,
`cargo fmt --all -- --check`, `cargo clippy --workspace --all-targets
--all-features --locked -- -D warnings`, `cargo test --workspace
--all-features --locked` (3226+ pass, 0 fail).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/tencent-lighthouse/doctor.sh

@@ -109,7 +109,7 @@ check_binaries() {
   fi
   if [[ -x "${tui}" ]]; then
     pass "${tui} is executable"
-    "${tui}" --version 2>/dev/null | sed 's/^/[info] deepseek-tui version: /' || warn "deepseek-tui --version failed"
+    "${tui}" --version 2>/dev/null | sed 's/^/[info] codewhale-tui version: /' || warn "codewhale-tui --version failed"
   else
     fail "${tui} is missing or not executable"
   fi