docs(pregate): Playwright missing-browsers exception and literals continuation rule

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

changelog.d/gsta-212-pregate-runners.md

@@ -2,9 +2,9 @@
 
 ### Fixed
 - **Missing pytest is the machine's gap.** Before planning `python3 -m pytest`, `lanes` asks that python3 whether it can import pytest (10 s probe, from the repo root). If it can't, the file is unclaimed and the lane is `PREGATE_ENVIRONMENT` (missing-binary, `pytest` or `python3`): "install pytest on this machine and rerun, or run the lane remotely; the diff is not at fault".
-- **Playwright specs run under Playwright.** A JS/TS test file that imports `@playwright/test` at the start of a line runs as `<pm exec> playwright test --reporter=list` from its nearest package. Other tests keep their runner. A declared `runner` still takes every file. Playwright's summary is read count line by count line: failed and interrupted count as failed, flaky and passed as passed, skipped as not run. A run where every test fails and Playwright says its browser is not installed is `PREGATE_ENVIRONMENT` naming `npx playwright install`.
+- **Playwright specs run under Playwright.** A JS/TS test file that imports `@playwright/test` at the start of a line runs as `<pm exec> playwright test --reporter=list` from its nearest package. Other tests keep their runner. A declared `runner` still takes every file. Playwright's summary is read count line by count line. Failed and interrupted count as failed, flaky and passed as passed, and skipped as not run. A run where every test fails and Playwright says its browser is not installed is `PREGATE_ENVIRONMENT` naming `npx playwright install`.
 - **Mixed-language root tests each get a runner.** A repo's bun, vitest or jest now claims only JS/TS files. When no one runner fits every root test, they are split by language and each part is detected on its own. So `.mjs` with `.py` runs `node --test` and pytest, and a `.py` test in a vitest repo gets pytest instead of vitest. `gstack-pregate init` drops its "a selection mixing these languages needs runner set" note.
 - **`literals` binds a one-character old value to its statement.** The value counts on a line that names the constant, or on up to three lines that continue that statement, never on a comment line. Version-history rows count as before. A lowercase call-site name (`attempts`, `limit`) also needs the changed module named in the file. Values of two or more characters are unchanged.
 
 ### Changed
-- **docs/pregate.md** describes the new detection and the literals binding. **docs/state-root.md** lists `pregate/runs/<run id>/`.
+- **docs/pregate.md** describes the new detection and the literals binding. **docs/troubleshooting.md** names the Playwright missing-browsers case under `PREGATE_ENVIRONMENT`. **docs/state-root.md** lists `pregate/runs/<run id>/`.

docs/pregate.md

@@ -195,8 +195,8 @@ Two stages with separate clocks, both printed:
   lines are not recognized as history rows.
   A one-character old value (`2`) counts only in a statement that names the
   constant: on the name's line, or on up to three lines that continue it (the
-  line before ends with `(`, `,`, `.`, `=` or another operator, or the line
-  starts with `.`, `)` or `]`), never on a comment line, plus the history rows
+  line before ends with `(`, `[`, `{`, `,`, `.`, `=` or another operator, or the
+  line starts with `.`, `)`, `]`, `}` or an operator), never on a comment line, plus the history rows
   above. A `$2` in a shell stub, a comment, or `export default 2` in a fixture
   elsewhere in the file is not a consumer. A call-site name such as `attempts`
   or `limit` is an ordinary word, so for it the file must also name the changed
@@ -834,7 +834,7 @@ failure the branch caused carries `cause: "diff"` (`PREGATE_LANE_FAILED`,
 
 | Kind | Evidence |
 |---|---|
-| `missing-binary` | exit 127, `command not found`, a spawn `ENOENT`, a runner tool `not on PATH` (dart, flutter, cargo, a package manager) |
+| `missing-binary` | exit 127, `command not found`, a spawn `ENOENT`, a runner tool `not on PATH` (dart, flutter, cargo, a package manager, `python3`, or `pytest` when python3 cannot import it), Playwright's browsers not installed |
 | `network` | `ENOTFOUND`, `ECONNREFUSED`, `ECONNRESET`, `ETIMEDOUT`, `EAI_AGAIN`, `Could not resolve host`, `fetch failed`, a TLS handshake or certificate failure |
 | `quota` | `quota`, `429 Too Many Requests`, `rate limit`, `insufficient_quota` (a vCPU quota on the remote backend) |
 | `disk` | `ENOSPC`, `No space left on device`, `EDQUOT` |
@@ -845,7 +845,11 @@ The classifier is conservative. A local lane that exited non-zero is read from
 its output **only when its runner reported no test summary** (nothing ran) and
 the runner was not seen starting a test file; a run whose summary counts `N
 ran, M failed` is the diff's failure whatever its log says, so a test that
-failed on `ECONNREFUSED` is still a red test. A remote gate that exited
+failed on `ECONNREFUSED` is still a red test. One exception: when every
+failed run is a Playwright run in which every test failed and Playwright says
+its browsers are not installed, the lane is `missing-binary` with `proof:
+"output"` (a partial install, where some tests pass, stays the diff's
+failure). A remote gate that exited
 without a `PREGATE_REMOTE:` line is read from its **preamble only** (its first
 40 lines, before any test output could stream): a VM refused for quota or an
 unreachable API there never ran the tests, so it is environment and the

docs/troubleshooting.md

@@ -3555,7 +3555,10 @@ and the table prints `environment: <kind> — <evidence>`. A test that failed an
 whose log also names a connection error is **not** this code: the runner's own
 summary counted a failure, so it is `PREGATE_LANE_FAILED` with `cause:
 "diff"`; nor is a runner, guard or gate script whose own binary is present but
-exits 127. `proof: "launch"` is certain (the command could not start, its
+exits 127. One exception: a Playwright lane where every test failed and
+Playwright says its browsers are not installed is `missing-binary` with
+`proof: "output"` (`npx playwright install`); a partial install stays the
+diff's failure. `proof: "launch"` is certain (the command could not start, its
 binary is off PATH, the runtime or a gstack tool refused); `proof: "output"`
 means a rule matched the command's text before any test was counted, which the
 diff's own output could have written, so the line says `(inferred from output)`