Changelog, dev startup, README, AgentHub 0.4.0, model catalog, and landing site (#7)

Branch-length batch covering tooling, the model layer, the Web App and the public
surfaces. Highlights:

- Changelog: a per-release `changelog/<version>/` tree, grouped by the surface each
  change touches, with a root CHANGELOG.md holding one line per release.
- Dev startup: `scripts/dev-prebuild.mjs` serializes the skills+core prebuild behind a
  lock and keeps `pnpm install` current; `pnpm dev` runs server+web together.
- AgentHub 0.3.3 -> 0.4.0: OmniMessage complete payloads carry one opaque `fidelity`
  object in place of item-level `signature`/`phase`, threaded verbatim through Trace,
  replay and resume; malformed classification adapted to the new error types.
- Model layer: a model is always referenced by an explicit `(provider, model_id)` pair.
  The provider is never inferred, guessed or defaulted -- both the catalog inference and
  the unique-match config resolution are gone, and CLI, SDK, server routes and
  run_subagent all require the complete pair. Catalog gains the Qwen Token Plan, Qwen
  Pay-As-You-Go and Fireworks AI gateways, plus an expanded OpenRouter group.
- Web App: catalog preset sync and per-group speed test on the Models page, positional
  slash commands, a markdown renderer, skill-library update reminders, and a vertically
  centred draft page whose upward menus size themselves to the room available.
- Public surfaces: restructured READMEs, the penguin.ooo landing site and blog, refreshed
  benchmark results for both suites, and the demo videos playing on the landing page.

Includes the fixes from a full review of the branch: 23 confirmed findings, among them a
provider-inference bug that could send one vendor's API key to another vendor's endpoint,
and an Escape handler that destroyed the composer's contents unrecoverably.

Verified on the branch head: pnpm test (1127 passing, 7 packages), pnpm typecheck and
pnpm format:check clean, Playwright e2e 14/14.

packages/server/test/schedules.test.ts

@@ -146,17 +146,24 @@ describe("schedules api", () => {
     ).toBe(404);
   });
 
-  it("validation 400: period below the minimum, invalid instant, pick-one target, invalid task name", async () => {
+  it("validation 400: period below the minimum, invalid instant, pick-one target, half a model reference, invalid task name", async () => {
     const ok = { prompt: "p", enabled: false, startAt: FUTURE };
     const cases = [
       { name: "j1", ...ok, period: "4m" },
       { name: "j2", ...ok, startAt: "someday" },
       { name: "j3", ...ok, sessionId: "s", workspace: "/w" },
+      // A model reference is a pair: neither half alone is accepted (nothing is inferred).
+      { name: "j4", ...ok, modelId: "deepseek-v4-pro" },
+      { name: "j5", ...ok, provider: "deepseek" },
       { name: "bad.name", ...ok },
     ];
     for (const body of cases) {
       expect((await owner.post(base, body)).status, JSON.stringify(body)).toBe(400);
     }
+    // Nothing was persisted for any of them.
+    const list = (await (await owner.get(base)).json()) as SchedulesResponse;
+    expect(list.schedules).toEqual([]);
+    expect(list.invalidFiles).toEqual([]);
   });
 
   it("hand-edited files: invalid ones land in invalidFiles; expired one-shots are marked missed during reconciliation", async () => {
@@ -175,4 +182,22 @@ describe("schedules api", () => {
     // For a hand-edited file, the creator falls back to the Project owner.
     expect(stale?.creatorUserId).toBe("owner_a");
   });
+
+  it("a file holding model_id without provider lands in invalidFiles instead of being scheduled", async () => {
+    // What a schedule file persisted before the pairing rule looks like: the provider is
+    // never filled in for it, the file is simply reported invalid and skipped.
+    const dir = scheduleDir(t.root, projectId, "default_agent");
+    await fs.mkdir(dir, { recursive: true });
+    await fs.writeFile(
+      path.join(dir, "legacy.toml"),
+      `prompt = "p"\nenabled = true\nstart_at = "${FUTURE}"\nmodel_id = "deepseek-v4-pro"\n`,
+      "utf8",
+    );
+    const list = (await (await owner.get(base)).json()) as SchedulesResponse;
+    expect(list.schedules).toEqual([]);
+    expect(list.invalidFiles.map((f) => f.name)).toEqual(["legacy"]);
+    expect(list.invalidFiles[0]?.error).toContain("given together");
+    // Reading it by name reports the same error rather than 404 or a 500.
+    expect((await owner.get(`${base}/legacy`)).status).toBe(400);
+  });
 });