fix: align detection and init behavior across implementations

[danjdewhurst]

Fixes from a full repo review. The headline items are cross-implementation consistency bugs: identical inputs could produce different results in the TypeScript, Python, and Rust implementations, contrary to the portable detection contract.

Cross-implementation fixes (each pinned by new shared fixtures)

• Equal-confidence tie-break: Rust's max_by picked the last maximal match, while TS/Python picked the first. With CURSOR_AGENT=1 GEMINI_CLI=1, Rust reported gemini and TS/Python reported cursor. All implementations now prefer the earliest rule in the registry.
• Duplicate signals: a variable matching both an exact rule and a prefix rule (e.g. CURSOR_AGENT) was reported twice in signals. Results are now deduplicated.
• Prefix signal ordering: Rust sorted prefix-matched signal names; TS and Python emitted env insertion order. TS and Python now sort too.
• agenthint init --json: TS/Python printed AI_AGENT=--json (exit 0) while Rust exited 2. All CLIs now reject option-like names with the usage message and exit 2, and Rust's --help/init argument handling matches TS/Python exactly.
• Cowork explainability: when CLAUDE_CODE_IS_COWORK classifies the result as cowork, the classifier signal is now included in signals.

Cleanups

• TS: one shared AI_AGENT normalizer (src/agent-names.ts) for detection and init; removed the dead isKnownAgent branch. Public exports unchanged.
• Rust: use parent_id() instead of spawning ps to find the parent pid.
• Python: cache the detection-rules JSON instead of re-parsing per call.
• Node CLI test: compare stdoutContains fixtures literally (matching Rust/Python) instead of as regex.

Tooling and docs

• Build and install linux-arm64 native binaries (ubuntu-24.04-arm matrix entry + install.sh detection).
• Commit the up-to-date Cargo.lock, guard CI with cargo metadata --locked, and add the release-please cargo-workspace plugin so version bumps keep the lockfile in sync (worth eyeballing on the next release PR).
• Pin Python in .mise.toml so npm run check works out of the box.
• Document AGENTHINT_AGENT, the ordering/dedup/tie-break contract in SPEC, the REPL_ID false-positive caveat, and the Windows parent-process limitation.

Deliberately unchanged: REPL_ID still reports isAgent: true at 0.65 confidence — documented the threshold guidance instead of changing detection semantics.

https://claude.ai/code/session_01R7u5FuNixEbMNQiFGBBx3H

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ℹ️ Review info

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Configuration used: Organization UI

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📥 Commits

Reviewing files that changed from the base of the PR and between 3beb9d5 and 169555e.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (19)

• .github/release-please-config.json
• .github/workflows/ci.yml
• .github/workflows/native-binaries.yml
• .mise.toml
• README.md
• SPEC.md
• crates/agenthint/src/lib.rs
• crates/agenthint/src/main.rs
• docs/signals.md
• fixtures/cli-cases.json
• fixtures/detection-cases.json
• install.sh
• python/agenthint/__init__.py
• python/agenthint/cli.py
• src/agent-names.ts
• src/cli.ts
• src/index.ts
• src/init.ts
• test/cli.test.mjs

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