feat(chrome): hand snapshots to context mode

pi-chrome/test-suite/notes/runner-spec.md

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+# Recipe runner spec
+
+Future Node/Pi runner should:
+
+1. Read `manifest.json`.
+2. Probe environment capabilities (`trusted`, `clipboard`, `touch`, `dialogs`, `downloads`, `fileSystem`, `strictCspFallback`).
+3. For each entry:
+   - read `gate` (`core`, `conditional`, `quality`) and score in that bucket
+   - skip if `requires` is unsatisfied and expected is `CONDITIONAL`
+   - navigate to challenge URL
+   - execute `recipe` in order
+   - wait `verdictDelayMs || 500`
+   - evaluate `JSON.stringify({v:window.__verdict,r:window.__reason,d:window.Challenge?.state?.details,e:window.__events?.slice(-20)})`, except strict-CSP pages where eval is expected to fail; read persisted verdict from dashboard/localStorage after leaving the CSP page
+   - compare to `expected[mode]`
+4. Output:
+   - Markdown summary
+   - JSON details
+   - JUnit XML for CI
+
+Runner must adapt recipe intent:
+
+- expand `${REPO_ROOT}` path placeholders
+- adapt unsupported shadow/iframe selector notation to snapshot uids or evaluate fallback
+- preserve hook install ordering for console/network capture tests
+- substitute dynamic tab ids from `chrome_tab list` recipes
+- support screenshot/coordinate fallback for strict CSP pages where snapshot/evaluate are blocked
+- record whether trusted/CDP path was used
+
+Long-horizon task runner should read `task-manifest.json`, replace `$RUN_ID`, solve task, then evaluate task grader expression.