Finish Phase 22: the half of Petal that works with the tunnel down

Grammar lite, the false-friend list, the daily invitation and the offline
miscollocations — the four remaining §5–§6 items, all client-side and all
alive on a box that cannot reach the model.

The offline collocations forced a schema change. `type` had been doubling
as the answer to "which engine found this" — `mechanics` meant offline —
and that stops being true the moment an offline rule proposes a
collocation. Migration 0013 adds `source` (llm | local) and every pass now
scopes its DELETE by engine; without it the coach silently wiped every
offline chunk on the page. Existing rows backfill by type, so a pre-0013
collocation row is claimed as the coach's, which it was: the offline list
did not exist yet.

The rule pack is hand-curated rather than mined, and the entries left out
are the point — `married with` is wrong until "married with children",
`arrive to` wants at or in depending on the noun. A pack running on every
keystroke must not correct correct writing.

Claude-Session: https://claude.ai/code/session_016y6gyuHkQXPiEuW8RGQyua

web/src/i18n/i18n.test.ts

@@ -220,3 +220,43 @@ describe('the pt-PT pack', () => {
     expect(ptPT.editor.alsoIn).not.toBe(zh.editor.alsoIn)
   })
 })
+
+// False friends are a per-pair dataset rather than copy: the Latin pairs carry
+// the traps their writers actually fall into, and the zh pair legitimately has
+// none. Both halves of that are worth pinning.
+describe('false friends', () => {
+  it('the zh pair has none, because the trap needs a shared script', () => {
+    expect(Object.keys(zh.falseFriends)).toHaveLength(0)
+  })
+
+  it('the pt-PT pair carries the ones that cost most', () => {
+    // Not an exhaustive list — these are the four every European Portuguese
+    // speaker meets in their first month of writing English.
+    for (const word of ['actually', 'pretend', 'realize', 'library']) {
+      expect(ptPT.falseFriends[word], word).toBeDefined()
+    }
+    expect(Object.keys(ptPT.falseFriends).length).toBeGreaterThan(10)
+  })
+
+  it('is keyed by the lowercase English word, so a lookup can find it', () => {
+    for (const p of PACKS) {
+      for (const key of Object.keys(p.falseFriends)) {
+        expect(key, `${p.code}: "${key}" must be lowercase`).toBe(key.toLowerCase())
+        expect(p.falseFriends[key].native.trim(), key).not.toBe('')
+        expect(p.falseFriends[key].en.trim(), key).not.toBe('')
+      }
+    }
+  })
+
+  // The heads-up must never read as an accusation: she may well have meant the
+  // word. It says what the English one means and stops there.
+  it('never tells her she is wrong', () => {
+    const forbidden = /wrong|mistake|error|incorrect|don't use|do not use|errado|erro|incorrecto/i
+    for (const p of PACKS) {
+      for (const [key, line] of Object.entries(p.falseFriends)) {
+        expect(line.native, `${p.code}/${key}`).not.toMatch(forbidden)
+        expect(line.en, `${p.code}/${key}`).not.toMatch(forbidden)
+      }
+    }
+  })
+})