Add the no-hardcoded-tunables convention and its review check

A number or string that two reasonable deployments could want set
differently — a timeout, grace period, output cap, result-count limit,
model name, base URL — belongs on the plugin's schemastery Config with
the shipped value as its default, not in a bare literal or module
constant. A DEFAULT_* constant or a test-only injection seam is not
configurability: the test is whether a cordis.yml deployment can change
the value without a code edit. Protocol/wire constants, semantic
constants, values pinned by an external spec, and security invariants
stay hardcoded.

The convention lands in AGENTS.md § Conventions (the authoritative
source the review skill cites); dsh-code-review gains the matching
reviewer-only check, since no mechanical gate can detect a hardcoded
tunable.

.agents/skills/dsh-code-review/SKILL.md

@@ -21,7 +21,7 @@ Independent judgment governs *what to look at* and *how to apply a rule to this
 
 These define the conventions and gates this repo is checked against, and they are authoritative. Read them at the source so this skill never drifts out of sync — and apply judgment in *interpreting* them for the case at hand, not in deciding whether they apply.
 
-- **[AGENTS.md](../../../AGENTS.md) § Conventions** — effect-based registrations, declaration-merging for events/ctx keys, waterfall `next()` discipline, discriminated-union match-don't-chain, explicit-over-implicit at seams, the empty-`catch` rule, symmetry.
+- **[AGENTS.md](../../../AGENTS.md) § Conventions** — effect-based registrations, declaration-merging for events/ctx keys, waterfall `next()` discipline, discriminated-union match-don't-chain, explicit-over-implicit at seams, no hardcoded tunables in plugins, the empty-`catch` rule, symmetry.
 - **AGENTS.md § Defensive patterns (hard-won)** — each bullet is a bug class that bit us. Reviewing anything touching process lifecycle, async/await, disposal, or adapter error paths? Re-read this first — then look for the *adjacent* mistake it doesn't name.
 - **AGENTS.md § Type Safety and Documentation** — the doc-sync rule (code change ⇒ update README + JSDoc in the SAME commit) and the no-hard-wrap markdown convention.
 - **[packages/AGENTS.md](../../../packages/AGENTS.md)** — per-package conventions (file layout, the HMR-safety test requirement).
@@ -44,6 +44,7 @@ Where your independent reasoning earns its keep. Start here, then keep going acr
 - **e2e verifies the world, not the agent's self-report.** For real-API tests, confirm the assertion re-runs the command/checks the file externally — a keyword probe lets a cheating agent pass (see AGENTS.md e2e bullet). For a behavior change to the agent's real flows, a no-key/mock test alone is usually insufficient: a with-key e2e (especially a smoke test that boots the real example and checks the world) is cheap here and catches "green units, broken product" — encourage it rather than treating real-API tests as expensive (see AGENTS.md § Secrets / .env).
 - **Plugin export shape + real-loader coverage.** A new/changed `cordis.yml`-loaded plugin: is it a function/namespace plugin (`name`/`inject`/`Config`/`apply` named exports) with NO `export default`? A stray default export makes the Loader's `unwrapExports` drop `inject` and the plugin crashes at load with `cannot get property … without inject` — invisible to hand-built `ctx.plugin({...})` tests and to line coverage. Confirm there's a test driving it through the REAL loader path (the no-key subprocess e2e for ACP is the model). And any opportunistic read of a service NOT in `static inject` should use `ctx.get(name)`, not `ctx.<name>` (the property proxy throws through a foreign shadow). See [packages/AGENTS.md](../../../packages/AGENTS.md) and [docs/postmortem/0001](../../../docs/postmortem/0001-acp-default-export-drops-inject.md).
 - **Seam discipline.** New swappable capability? Check it's split per the capability-seams RFC (interface / impl / consumer), and that the consumer injects the interface key, never an implementation type.
+- **Hardcoded tunables that should be plugin config.** A literal timeout, grace period, output/truncation cap, result-count limit, retry count, buffer size, model name, API base URL, user agent, or filesystem path introduced inside a plugin belongs on the plugin's schemastery `Config` with the shipped value as its default (AGENTS.md § Conventions "No hardcoded tunables in plugins"). A named `DEFAULT_*` constant or a test-only injection seam is not configurability — the question to ask is whether a `cordis.yml` deployment can change the value without a code edit. Protocol/wire constants, semantic constants, values pinned by an external spec, and security invariants are exempt; a new `Config` field also needs its README row and range validation. No gate detects a hardcoded tunable — this check is entirely on the reviewer.
 - **Test quality — sufficiency, not just coverage.** 100% per-file coverage and a green suite are necessary, not sufficient: they prove the lines *ran*, not that the feature *works the way it ships*. Judge whether the tests are sufficient on two axes. (1) **Would they fail if the behavior regressed?** A test that passes but asserts the wrong thing — or restates the implementation instead of the contract (events fired, disposal reached, the world changed) — is worse than none. (2) **Do they exercise the REAL thing, the way it's actually used?** Prefer the genuine collaborator over a fake, drive the change through its real entry path (the cordis Loader, the ACP bridge, a booted subprocess — not a hand-built `ctx.plugin({...})` that bypasses `unwrapExports`), and verify the WORLD (re-read the file/log/registry externally), not the agent's self-report. A test that fakes the inputs just enough to cover every line will agree with whatever the author assumed; the real thing won't. When a test sets up a *clean/happy* path to reach a line, ask whether the line's PURPOSE is exercised — e.g. a durability/teardown path "tested" by a fully-completed turn never proves the mid-flight teardown it exists for; a torn-tail recovery branch covered by a well-formed log never proves recovery. Flag tests that hit the line but not the scenario. See AGENTS.md § Defensive patterns "Line coverage is not behavior coverage" and "Prefer the REAL implementation over a mock/stand-in in tests".
 - **Snapshot coverage for transcript/UX changes.** If the PR changes the editor-facing transcript or end-to-end agent UX — the ACP bridge's event→update translation, the agent loop's observable output, tool presentation, or anything an editor renders — it must add or update a snapshot scenario (`examples/*/tests/**/*.snapshot.ts`, goldens under `examples/acp-agent/tests/snapshots/`) or note explicitly why none applies (AGENTS.md § Conventions). Review the golden diff itself: a changed `stdout.golden.txt` / `session.golden.txt` is a behavior change in disguise — confirm it's intended, not an accidental regression someone re-recorded away. A pure internal refactor with no observable-output change is exempt, but the PR should say so. See [docs/rfc/implemented/testing/2026-06-19-acp-snapshot-tests.md](../../../docs/rfc/implemented/testing/2026-06-19-acp-snapshot-tests.md).
 - **Bilingual docs: review translation quality, not just pairing.** If the PR adds or edits a doc pair, read the changed English and Chinese sides and compare the meaning, not only the mechanical diff. Verify terms against [terminology.md](../../../docs/i18n/terminology.md), including first-occurrence annotations and "do not translate as" prohibitions; if a new term has no established precedent, the PR should keep it in English, list it under `待定术语`, and update the terminology table once the rendering is decided. A green `verify-translation-pairing` only proves hashes, switchers, and structure were recorded — it does not prove the translation is faithful, natural, or correctly termed. Treat [translation-rules.md](../../../docs/i18n/translation-rules.md) MUST/MUST NOT violations as blocking.