feat: detect goose, junie, pi, and kiro agents

[tknickman]

Summary

Adds four agents from the unjs/std-env list that we were missing, and broadens opencode detection.

Agent	Detection
goose (Block)	GOOSE_PROVIDER set
junie (JetBrains)	JUNIE_DATA or JUNIE_SHIM_PATH set
pi	PATH matches \.pi[\\/]agent
kiro (AWS)	TERM_PROGRAM matches kiro and stdout is not a TTY

opencode now matches OPENCODE in addition to our existing OPENCODE_CLIENT (std-env checks OPENCODE).

New spec capabilities

goose and junie fit the existing schema. pi and kiro needed two new leaf condition types, added to agents.schema.json, src/types.ts, and the evaluator:

• env_matches — regex match against an env var ({ type, name, pattern }). pattern is a regex source string, substring semantics, case-sensitive; unset var or invalid pattern → no match (never throws).
• no_tty — matches when the process is non-interactive (!process.stdout.isTTY). This is the first leaf that reads runtime process state rather than env/filesystem; it exists so terminal-based IDE agents can be disambiguated from a human at the same terminal. kiro pairs env_matches on TERM_PROGRAM with no_tty — this is exactly the case std-env's issue #185 addressed. Documented as a deliberate exception in the schema.

Notes

• agents.json reformats from minified to pretty-printed (oxfmt, the project formatter, enforces this) — hence the larger-than-expected diff on that file.
• No changeset included: the Changesets setup (ci: set up automated releases with Changesets #3) isn't merged to main yet, so there's no .changeset/ infra here. Once ci: set up automated releases with Changesets #3 lands, this should get a minor changeset (new features, additive/backward-compatible), or be versioned accordingly at release.

Verification

• pnpm type-check, pnpm lint, pnpm format:check all pass.
• pnpm test — 86 tests pass (was 68). New unit tests for env_matches/no_tty, detection tests for all four agents (including kiro TTY vs no-TTY) and opencode via OPENCODE.
• pnpm build, then smoke-tested the built dist/ with real env vars: goose/junie/pi/opencode detected; kiro detected when piped (no TTY) and not detected under an emulated TTY.

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