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/cli/src/commands/run.ts

@@ -1,14 +1,14 @@
 /**
  * `penguin run` — send a single Task in one shot.
  *
- *   penguin run -m <msg> [--model-id <id>] [--provider <group>] [--workspace <path>]
+ *   penguin run -m <msg> [--model-id <id> --provider <group>] [--workspace <path>]
  *               [--project-id <id>] [--agent-id <id>]
  *               [--approve <allow-all|deny-all|read-only|always-ask>]
  *
  * Uses the current directory when Workspace is unspecified; uses the Project's default model
- * when model is unspecified. `--provider` is optional: when omitted, `--model-id` is resolved
- * via resolveModelRef semantics (only matches when the exact value is globally unique in the
- * config; ambiguity is an error). Defaults to interactive per-call approval; `--approve`
+ * when model is unspecified. A model reference is always an explicit `(provider, model_id)`
+ * pair, so `--model-id` and `--provider` must be given together — giving only one of them is
+ * an error, never a lookup. Defaults to interactive per-call approval; `--approve`
  * selects the permission mode.
  * Docs: /docs/cli § "penguin run".
  */
@@ -31,6 +31,14 @@ export function registerRunCommand(program: Command, t: Messages): void {
     .option("--workspace <path>", t.common.workspace)
     .option("--approve <mode>", t.common.approve)
     .action(async (opts) => {
+      // The model reference is a pair: commander can only require each option on its own,
+      // so the "both or neither" rule is enforced here. Giving neither is the normal case
+      // and falls back to the Project's default model.
+      if (Boolean(opts.modelId) !== Boolean(opts.provider)) {
+        process.stderr.write(`${t.error(t.modelRefIncomplete())}\n`);
+        process.exitCode = 1;
+        return;
+      }
       const mode = resolveApprovalMode(opts.approve, t);
 
       const agent = await createAgent({