Codewhale agent support (detection manifest + wiring)

[atmosuwiryo]

Codewhale agent support (detection manifest + wiring)

Implements the request in #1314. Status: contributed branch proposed
upstream — not merged or shipped yet.

I've built and locally tested herdr detection for
codewhale, a Rust/TUI terminal
coding agent. Posting here rather than opening a PR, since herdr's
contribution policy requires approved-contributor status for implementation
PRs. Happy to iterate on feedback, adjust scope, or hand this over to a
maintainer-controlled agent.

What it does

Herdr gains a codewhale agent kind with idle / working / blocked states:

• working — braille spinner strip (▌⣤ working · Nm · Esc to interrupt)
  plus OSC title (🐳 working…, 🐳 using tool…)
• blocked — Do you want to proceed? + numbered allow/deny options,
  plus the 🐳 waiting on you… title
• idle — ❯ composer prompt, guarded against the working/blocked rows
  with not-clauses

Manifest signals: OSC 0 window title (🐳 <verb>… while busy,
🐳 waiting on you… when blocked, Codewhale / ✓ done at rest), OSC 9;4
taskbar progress (4;1 busy / 4;0 clear), and screen fallbacks for all
three states.

Scope

• Agent::Codewhale enum variant + process-name identification
• src/detect/manifests/codewhale.toml (new)
• per-agent sound overrides, cjk_ime_agents docs
• website agent-detection catalog (index.toml + codewhale.toml)
• docs: agents table, agent start --kind lists, changelog — en/ja/zh-cn

Evidence and verification

• Manifest built from real screen evidence: a live detection-buffer capture
  from a codewhale session running inside herdr, plus codewhale's TUI source
  for the OSC title lifecycle and approval strings
• Validated with herdr agent explain --file — all three states correct
• 99 detect:: tests pass, including 5 new codewhale tests (idle/working/
  blocked + OSC title/progress rules)
• 93 maintenance script tests pass (manifest check, changelog,
  config-reference, docs parity)
• cargo fmt --check clean; tested locally inside herdr

Note: two gates I could not run green in my sandbox — clippy -D warnings
and the Windows target lint — fail identically on clean master (pre-existing
lints from a newer local Rust toolchain), not from this change.

Where the code lives

• Branch feat/codewhale-agent in my fork (no PR opened):
  https://github.com/atmosuwiryo/herdr/tree/feat/codewhale-agent
• Commit 97d1c9f9 — feat: add codewhale agent support, 19 files, +301/−9

Happy to adjust anything. Questions welcome.