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/docs/src/lib/strings-en.ts

@@ -6,7 +6,13 @@ export const en: Strings = {
   docsBadge: "Docs",
 
   nav: {
-    home: "Website",
+    highlights: "Highlights",
+    quickstart: "Quick start",
+    benchmark: "Benchmark",
+    contract: "CONTRACT.md",
+    features: "Features",
+    blog: "Blog",
+    docs: "Docs",
     github: "GitHub",
     openMenu: "Open navigation",
     closeMenu: "Close navigation",

packages/docs/src/lib/strings.ts

@@ -10,7 +10,15 @@ export const zh = {
   docsBadge: "Docs",
 
   nav: {
-    home: "产品主页",
+    // Landing-parity labels: the top bar mirrors the landing page's nav exactly
+    // (same items, same order) so the two sites link into each other seamlessly.
+    highlights: "特色",
+    quickstart: "快速开始",
+    benchmark: "评测",
+    contract: "CONTRACT.md",
+    features: "功能",
+    blog: "博客",
+    docs: "文档",
     github: "GitHub",
     openMenu: "打开目录",
     closeMenu: "关闭目录",