feat: proposals en registry

Añade sistema de proposals al registry: modelos (ProposalKind, ProposalStatus),
CRUD completo (Insert/Get/Update/Delete/List/Search con FTS), validación,
migración 002_proposals.sql y subcomando CLI fn proposal (add/list/show/update).
Motor de migraciones con embed.FS reemplaza schema estático.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

registry/migrations/002_proposals.sql

@@ -0,0 +1,42 @@
+-- Proposals table: agent-generated improvement suggestions for the registry.
+-- Lives in registry (not operations) because proposals benefit all projects.
+
+CREATE TABLE IF NOT EXISTS proposals (
+	id          TEXT PRIMARY KEY,
+	kind        TEXT NOT NULL CHECK(kind IN ('new_function','new_type','improve_function','improve_type','new_pipeline')),
+	target_id   TEXT NOT NULL DEFAULT '',
+	title       TEXT NOT NULL,
+	description TEXT NOT NULL DEFAULT '',
+	evidence    TEXT NOT NULL DEFAULT '{}',
+	status      TEXT NOT NULL DEFAULT 'pending' CHECK(status IN ('pending','approved','rejected','implemented')),
+	created_by  TEXT NOT NULL DEFAULT '',
+	reviewed_by TEXT NOT NULL DEFAULT '',
+	created_at  TEXT NOT NULL,
+	updated_at  TEXT NOT NULL
+);
+
+CREATE VIRTUAL TABLE IF NOT EXISTS proposals_fts USING fts5(
+	id,
+	title,
+	description,
+	evidence,
+	content='proposals',
+	content_rowid='rowid'
+);
+
+CREATE TRIGGER IF NOT EXISTS proposals_ai AFTER INSERT ON proposals BEGIN
+	INSERT INTO proposals_fts(rowid, id, title, description, evidence)
+	VALUES (new.rowid, new.id, new.title, new.description, new.evidence);
+END;
+
+CREATE TRIGGER IF NOT EXISTS proposals_ad AFTER DELETE ON proposals BEGIN
+	INSERT INTO proposals_fts(proposals_fts, rowid, id, title, description, evidence)
+	VALUES ('delete', old.rowid, old.id, old.title, old.description, old.evidence);
+END;
+
+CREATE TRIGGER IF NOT EXISTS proposals_au AFTER UPDATE ON proposals BEGIN
+	INSERT INTO proposals_fts(proposals_fts, rowid, id, title, description, evidence)
+	VALUES ('delete', old.rowid, old.id, old.title, old.description, old.evidence);
+	INSERT INTO proposals_fts(rowid, id, title, description, evidence)
+	VALUES (new.rowid, new.id, new.title, new.description, new.evidence);
+END;