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

internal/db/db.go

@@ -477,6 +477,26 @@ CREATE TABLE personal_words (
 ALTER TABLE suggestions ADD COLUMN resolved_at DATETIME;
 UPDATE suggestions SET resolved_at = created_at WHERE status != 'pending';
 CREATE INDEX idx_suggestions_resolved ON suggestions(status, resolved_at);
+`,
+		},
+		{
+			// Which engine proposed a row. Until now `type` doubled as that answer —
+			// 'mechanics' meant "the offline rule pack found this" and everything else
+			// meant "the model did". That breaks the moment an offline rule proposes a
+			// *collocation*: the miscollocation list (SUGGESTIONS §6) is the same
+			// family, the same rail and the same warm phrasing as the LLM coach, and it
+			// must stay type='collocation' so an accepted chunk still plants in the
+			// garden and still counts in the journal. With type no longer naming the
+			// engine, the two passes could not scope their own DELETEs — the coach
+			// would wipe the offline flags, and the offline pass would leave the
+			// coach's behind to accumulate.
+			//
+			// Existing mechanics rows are local by definition; everything else came
+			// from a model.
+			name: "0013_suggestion_source",
+			stmt: `
+ALTER TABLE suggestions ADD COLUMN source TEXT NOT NULL DEFAULT 'llm';
+UPDATE suggestions SET source = 'local' WHERE type = 'mechanics';
 `,
 		},
 	}