test(native-chat): ratchet the retired provider-exit copy out of production

The retirement filter hides a status row on two facts: a restart-eviction item
id and copy that opens with the retired prefix. The identity half is still
minted today, so the filter cannot tell a new producer's row from the legacy row
it exists to hide — any future writer of that copy would be dropped from every
transcript with no trace. Until now that safety property lived only in a doc
comment.

Scan the shipped tree for a string literal that OPENS with the retired prefix,
which is exactly what the filter's `startsWith` reads. Comments are stripped
first, so prose about the retirement is not a producer, and the filter's own
constant is exempt. Tests are excluded: writing the copy is how the filter is
exercised.

src/main/native-chat/agent-session-wire/agent-session-retired-provider-exit-copy-ratchet.test.ts

@@ -0,0 +1,86 @@
+import { join, resolve } from 'node:path'
+import { describe, expect, it } from 'vitest'
+import { scanSourceTree, stripComments } from '../../../shared/source-scan/source-tree-scan'
+
+/**
+ * The retired copy has to stay retired.
+ *
+ * `withoutRetiredProviderExitStatusItems` hides a status row on TWO facts: a
+ * `restart-eviction:<sessionId>:<fence>` item id, and copy that starts with the retired prefix.
+ * The identity half is still minted today, so the filter cannot tell a new producer's row from
+ * the legacy row it exists to hide — anything that writes this copy again would be dropped from
+ * every transcript with no trace. No production writer is left, and this is what keeps it so.
+ *
+ * Deliberately narrow: only a literal that OPENS with the prefix, which is exactly what the
+ * filter's `startsWith` reads. Prose about the retirement is not a producer.
+ */
+
+const RETIRED_COPY_PREFIX = 'Provider exited'
+
+/** The filter compares against the prefix rather than writing it, so it owns the one literal. */
+const FILTER_SOURCE_PATH =
+  'main/native-chat/agent-session-wire/agent-session-retired-provider-exit-status-filter.ts'
+
+/** Line numbers of string literals whose first character begins the retired copy. */
+export function findRetiredProviderExitCopyLines(source: string): number[] {
+  const code = stripComments(source)
+  const pattern = new RegExp(`['"\`]${RETIRED_COPY_PREFIX}`, 'g')
+  return [...code.matchAll(pattern)].map((match) => code.slice(0, match.index).split('\n').length)
+}
+
+describe('retired provider-exit copy ratchet', () => {
+  it('flags a literal that opens with the retired copy', () => {
+    const flagged = [
+      `const text = 'Provider exited: recorded pid absent on host'`,
+      `appendStatus("Provider exited")`,
+      'appendStatus(`Provider exited: ${reason}`)'
+    ]
+    for (const source of flagged) {
+      expect(findRetiredProviderExitCopyLines(source), source).toHaveLength(1)
+    }
+  })
+
+  it('reports the line the literal sits on', () => {
+    expect(findRetiredProviderExitCopyLines(`const a = 1\n\nconst b = 'Provider exited'`)).toEqual([
+      3
+    ])
+  })
+
+  it('leaves prose and unrelated copy alone', () => {
+    const allowed = [
+      `// the old bare 'Provider exited: <reason>' row`,
+      `/* wrote \`Provider exited\` once */`,
+      `const text = 'provider exited'`,
+      `const text = 'The provider exited unexpectedly'`,
+      `const text = 'Provider exit was not proven'`,
+      `if (text.startsWith(prefix)) {}`
+    ]
+    for (const source of allowed) {
+      expect(findRetiredProviderExitCopyLines(source), source).toEqual([])
+    }
+  })
+
+  const repoRoot = resolve(__dirname, '..', '..', '..', '..')
+  // Tests write the retired copy on purpose: that is how the filter is exercised.
+  const files = scanSourceTree(join(repoRoot, 'src'))
+
+  it('scans a plausible number of files', () => {
+    // A broken root or extension list would make the guard silently vacuous.
+    expect(files.length).toBeGreaterThan(500)
+  })
+
+  it('has no production writer of the retired copy', () => {
+    const offenders = files
+      .filter(({ relativePath }) => relativePath !== FILTER_SOURCE_PATH)
+      .flatMap(({ relativePath, source }) =>
+        findRetiredProviderExitCopyLines(source).map((line) => `src/${relativePath}:${line}`)
+      )
+    expect(
+      offenders,
+      `A status row whose copy opens with "${RETIRED_COPY_PREFIX}" is hidden from every transcript by ` +
+        'agent-session-retired-provider-exit-status-filter.ts whenever it also carries a ' +
+        'restart-eviction identity, which is still minted. Write the outcome copy the death ' +
+        'evidence decides instead of resurrecting the retired prefix.'
+    ).toEqual([])
+  })
+})