docs: add CodeWhale to supported agents (native AGENTS.md reader, zero setup)

[ousamabenyounes]

Adds CodeWhale to the supported-agents list. CodeWhale (the rebranded DeepSeek-TUI, 38k★, Rust) reads AGENTS.md from the project root natively — ponytail works with zero adapter file.

What changes

• README: agent badge 13 → 14, a ### CodeWhale install section, and CodeWhale added to the instruction-only adapter list.
• docs/agent-portability.md: one table row for CodeWhale.

Docs-only. No code.

Why it's accurate

CodeWhale's own docs/CONFIGURATION.md: "AGENTS.md — cross-agent project instructions … the canonical file … CLAUDE.md and .claude/instructions.md are read as compatibility fallbacks." Loader: crates/tui/src/project_context.rs::load_project_context reads AGENTS.md from the workspace root and as_system_block() wraps it as <project_instructions> for the system prompt.

I dropped an earlier "~/.codewhale/AGENTS.md for global use" line: the installed binary (v0.8.61) still resolves the global path to ~/.deepseek/AGENTS.md (rename incomplete), so that claim was wrong. Only the verified project-root path is documented.

Test verification (RED → GREEN)

Installed CodeWhale 0.8.61 (npm i -g codewhale) and added a test to CodeWhale's own loader that drops ponytail's real AGENTS.md into a workspace root and asserts CodeWhale ingests it into the <project_instructions> block.

The test (in crates/tui/src/project_context.rs):

#[test]
fn test_load_real_ponytail_overlay() {
    let src = std::env::var("PONYTAIL_AGENTS_MD")
        .expect("set PONYTAIL_AGENTS_MD to the ponytail AGENTS.md path");
    let overlay = fs::read_to_string(&src).expect("read ponytail AGENTS.md");

    let tmp = tempdir().expect("tempdir");
    fs::write(tmp.path().join("AGENTS.md"), &overlay).expect("write");

    let ctx = load_project_context(tmp.path());

    assert!(ctx.has_instructions(), "overlay not loaded");
    let block = ctx.as_system_block().expect("system block");
    assert!(block.starts_with("<project_instructions"), "not wrapped: {block:.80}");
    assert!(block.contains("lazy senior dev"), "ponytail signature missing");
}

GREEN — overlay written as AGENTS.md, CodeWhale discovers it natively:

$ PONYTAIL_AGENTS_MD=.../AGENTS.md cargo test -p deepseek-tui --bins test_load_real_ponytail_overlay
     Running unittests src/main.rs (target/debug/deps/deepseek_tui-4fcdc7140bad2d94)
test project_context::tests::test_load_real_ponytail_overlay ... ok
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 3221 filtered out; finished in 0.00s

RED — same test, overlay written as NOPE.md (a filename CodeWhale does not read) → native discovery misses it:

test project_context::tests::test_load_real_ponytail_overlay ... FAILED
---- project_context::tests::test_load_real_ponytail_overlay stdout ----
thread 'project_context::tests::test_load_real_ponytail_overlay' panicked at crates/tui/src/project_context.rs:734:9:
overlay not loaded
test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 3221 filtered out; finished in 0.00s

RED proves the green isn't a tautology — it's specifically the AGENTS.md filename CodeWhale keys on. Flipping the name back to AGENTS.md returns to GREEN.

🤖 Generated with Claude Code