docs: state that build output is never a lint/format/typecheck target

Adds an AGENTS.md rule under the pre-push gate naming the gated surface
(first-party source) and everything excluded from it (each client's build/,
web's dist/ and storybook-static/, coverage/, test-servers/build,
core/**/{build,dist}, *.tsbuildinfo), why gating generated output is harmful
even when it only warns, and the fact that the three coverage guards assert
the converse and so cannot catch this drift. Mirrored into
.github/copilot-instructions.md per the maintenance rules.

Signed-off-by: cliffhall <cliff@futurescale.com>

.github/copilot-instructions.md

@@ -103,6 +103,7 @@ Both exist and do different jobs. Theme files (`src/theme/<Component>.ts`) custo
 - `npm run format` before committing; **`npm run ci` before pushing** (`validate` → `coverage` → `verify:build-gate` → `smoke` → Storybook). `npm run validate` is the fast inner-loop check and is **not** a substitute — it runs `test`, not `test:coverage`, so it does zero coverage gating.
 - **A dependency bump must land in every install that declares it.** v2 is not a workspace — the root and each `clients/*` have their own `node_modules`, and a client's test project compiles `core/` and `test-servers/src` (which resolve from the **root**) alongside the client's own sources. Bumping a shared dependency in one manifest only puts two versions of it in one `tsc` program; for a recursive-generic surface like zod that exhausts the tsc heap (#1896). `verify:dep-lockstep` fails the build on this — it derives its candidates from what each `tsc` program actually resolves (`tsc --listFilesOnly`, keeping packages that reach one program from two installs), so a package reached only through another package's `.d.ts` counts too (#1965) — so a PR bumping a package the shared sources pull in should update the root **and every client that already lists it** — not every client unconditionally, since a package absent from an install can't skew and adding it there would be a spurious dependency.
 - **A test or smoke must not touch real user state.** The web smokes run against a throwaway catalog via the shared `scripts/lib/prod-web-server.mjs` helper, never the developer's `~/.mcp-inspector/mcp.json` (#1977); the cli/tui smokes drive a temp `--catalog`. A new smoke spawning its own server, or teardown that removes a work dir without first awaiting `stopChild` (the #1801 race — `child-cleanup.mjs` exports both halves and both are required), should be flagged.
+- **Build output is never a gate target.** Lint, format, and typecheck read first-party source only; everything a build writes (`clients/*/build`, `clients/web/dist`, `storybook-static`, `coverage`, `test-servers/build`, `core/**/{build,dist}`, `*.tsbuildinfo`) stays out via each scope's `globalIgnores`, `format` globs, and tsconfig `include`. Gating generated code reports defects in vendored third-party source that nobody can fix, and a rule promotion turns that warning into a `validate` failure (#2043). Flag a PR that adds a build location without ignoring it in the same change, that widens an ignore to silence a finding in first-party code, or that adds a build directory to a tsconfig `include` to make a generated `.d.ts` resolve. Note the coverage guards don't catch this — they assert source is *covered*, not that output is *excluded*.
 - **Every PR references an issue**, first body line `Closes #<ISSUE_NUMBER>`.
 - **Every PR carries exactly one version label**, `v1` or `v2`, matching its base branch.
 - **Commits carry a `Signed-off-by:` trailer.** The DCO check is a hard merge gate and fails on a single unsigned commit; it matches the trailer against the author *or* committer, and skips only merge and bot commits. Use `git commit -s` — note `format.signOff` does *not* sign `git commit` (only `format-patch`). Repairing pushed commits means `git rebase HEAD~<n> --signoff` + `git push --force-with-lease`; remediation commits are not enabled on this repo.