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/content/configuration.en.md

@@ -35,7 +35,7 @@ The openrouter, siliconflow, and custom groups speak the OpenAI-compatible proto
 
 ## Project config
 
-`<root>/<project>/.project_config.toml` is the Project's single config file: a hidden file written with mode 0600, with credentials inlined on the model entries. Model identity is always the `(provider, model_id)` pair — string concatenation is forbidden everywhere.
+`<root>/<project>/.project_config.toml` is the Project's single config file: a hidden file written with mode 0600, with credentials inlined on the model entries. Model identity is always the `(provider, model_id)` pair — string concatenation is forbidden everywhere, and every reference into this file carries both halves: the provider is never inferred from a bare `model_id`.
 
 | Field | Description |
 | --- | --- |
@@ -143,9 +143,11 @@ compaction:
 | `{{PLATFORM}}` | Runtime platform |
 | `{{OS_VERSION}}` | Operating system version |
 | `{{DATE}}` | Current date |
-| `{{CWD}}` | Workspace path |
-| `{{AGENT_ID}}` | Agent id |
 | `{{PROJECT_DIR}}` | Project directory |
+| `{{AGENT_ID}}` | Agent id |
+| `{{CWD}}` | Workspace path |
+| `{{PROVIDER}}` | Model provider group |
+| `{{MODEL_ID}}` | Upstream model id |
 | `{{SESSION_ID}}` | Session id |
 
 `agent_state/AGENTS.md` is the developer-editable instruction file, injected via `{{AGENTS_MD}}` and empty by default — it is also the file an optimizer edits most (see [Self-Improvement](/self-improvement)).
@@ -157,6 +159,7 @@ compaction:
 - Key names must match `^[A-Za-z_][A-Za-z0-9_]*$` (shell environment variable naming rules);
 - Values are injected only into tool subprocess environments and never enter the model context or the Trace;
 - Only key names are disclosed in the system prompt via `{{VAULT_KEYS}}`;
+- Saving through the Web/API invalidates the Agent's cached Session runtimes: the next Task on any of its Sessions re-resumes and runs with the new values; a Task already in flight keeps the values it started with (a direct CLI file edit reaches a running server only when a Session is next created or resumed);
 - Managed via `penguin config vault set/list/remove` or the Web Vault tab.
 
 ## Schedules
@@ -172,7 +175,7 @@ Each file `agent_state/schedule/<name>.toml` describes one scheduled task (the f
 | `end_at` | no | End time; must be later than `start_at` |
 | `session_id` | no | Bind to an existing Session; mutually exclusive with the three fields below |
 | `workspace` | no | Workspace for new-Session mode |
-| `provider` / `model_id` | no | Paired model reference for new-Session mode |
+| `provider` / `model_id` | no | Paired model reference for new-Session mode; write both or neither — a lone `model_id` is rejected, and with neither the Project's default model is used |
 
 ```toml
 prompt = "Check yesterday's builds and summarize the failures"