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/skills.test.ts

@@ -57,11 +57,10 @@ describe("skills api", () => {
     expect(res.status).toBe(200);
     const body = (await res.json()) as SkillLibraryResponse;
     expect(body.groups.map((g) => g.id)).toEqual([
-      "agent-development",
-      "data-analysis",
-      "penguin-development",
-      "web-development",
-      "software-engineering",
+      "office-productivity",
+      "software-development",
+      "ai-app-development",
+      "agent-tuning",
     ]);
     for (const group of body.groups) {
       expect(group.title.length).toBeGreaterThan(0);
@@ -71,20 +70,22 @@ describe("skills api", () => {
       expect("description" in group).toBe(false);
     }
     // Members within a group follow the SKILL_GROUPS list order (as ungrouped by loadSkillGroups).
-    expect(body.groups[0]!.skills.map((s) => s.name)).toEqual([
-      "agent-creation",
-      "benchmark-design",
-      "agent-evaluation",
-      "agent-optimization",
+    expect(body.groups[0]!.skills.map((s) => s.name)).toEqual(["data-analysis", "firecrawl"]);
+    expect(body.groups[1]!.skills.map((s) => s.name)).toEqual([
+      "web-design",
+      "software-engineering",
     ]);
-    expect(body.groups[1]!.skills.map((s) => s.name)).toEqual(["data-analysis"]);
     expect(body.groups[2]!.skills.map((s) => s.name)).toEqual([
       "penguin-sdk",
       "penguin-cli",
       "agenthub-models",
     ]);
-    expect(body.groups[3]!.skills.map((s) => s.name)).toEqual(["web-design"]);
-    expect(body.groups[4]!.skills.map((s) => s.name)).toEqual(["software-engineering"]);
+    expect(body.groups[3]!.skills.map((s) => s.name)).toEqual([
+      "agent-creation",
+      "benchmark-design",
+      "agent-evaluation",
+      "agent-optimization",
+    ]);
     const skills = body.groups.flatMap((g) => g.skills);
     for (const skill of skills) {
       expect(skill.name.length).toBeGreaterThan(0);