feat: phase3 sub-project 7 — agent protocol + sqlite storage

.changeset/phase3-agent-protocol.md

@@ -0,0 +1,13 @@
+---
+"@dawn-ai/sqlite-storage": minor
+"@dawn-ai/core": minor
+"@dawn-ai/cli": minor
+"@dawn-ai/langchain": minor
+---
+
+Add Agent Protocol HTTP endpoints backed by a Dawn-native SQLite checkpointer (phase-3 sub-project 7).
+
+- New `@dawn-ai/sqlite-storage` package: `sqliteCheckpointer` (a `BaseCheckpointSaver` over Node's built-in `node:sqlite`, no native deps) and `createThreadsStore`. Requires Node 22.13+ (where `node:sqlite` is available without the `--experimental-sqlite` flag).
+- `dawn.config.ts` gains `checkpointer` and `threadsStore` fields — both pluggable, with SQLite-backed defaults at `.dawn/checkpoints.sqlite` and `.dawn/threads.sqlite`.
+- The dev server's HTTP layer is reshaped to the Agent Protocol: `POST /threads`, `GET`/`DELETE /threads/{id}`, `POST /threads/{id}/runs/stream`, `POST /threads/{id}/runs/wait`, `GET /threads/{id}/state`, `POST /threads/{id}/resume`. The legacy `POST /runs/stream` is removed.
+- Conversation state and permission interrupts now survive a server restart. `MemorySaver` is removed from `@dawn-ai/langchain`; the checkpointer is supplied by the caller. Permission resume is state-based (reads the parked interrupt from the checkpoint) and resolves the route durably from thread metadata.

.github/workflows/ci.yml

@@ -41,7 +41,10 @@ jobs:
       - name: Setup Node.js
         uses: actions/setup-node@v6
         with:
-          node-version: 22.12.0
+          # 22.14.0 — node:sqlite (used by @dawn-ai/sqlite-storage) is only
+          # available without the --experimental-sqlite flag from 22.13+.
+          # Matches release.yml and the engines floor.
+          node-version: 22.14.0
           cache: pnpm
 
       - name: Install