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/skills.en.md

@@ -58,16 +58,17 @@ The built-in Skills, by group (the group manifest is `SKILL_GROUPS` in `packages
 
 | Group | Skill | Purpose |
 | --- | --- | --- |
-| Agent Development | `agent-creation` | Turn a user requirement into a concrete agent: write the target agent's AGENTS.md and install the skills it needs |
+| Office Productivity | `data-analysis` | Complete data-analysis tasks with bounded evidence inspection, explicit answer-changing decisions, native artifact handling and final output verification |
+| | `firecrawl` | Web search and page scraping into clean markdown via the Firecrawl API |
+| Software Development | `web-design` | Penguin visual language for generated web pages and app UIs: design tokens, components, light/dark themes and chat layouts |
+| | `software-engineering` | Complete software-engineering tasks: investigate and review code, implement fixes, features and refactors with minimal scope, validate changes, and report verified outcomes |
+| AI App Development | `penguin-sdk` | Build AI and RAG apps on the SDK: the createSession/run streaming loop plus a complete retrieval recipe with chunk-revealing citations |
+| | `penguin-cli` | Manage model API keys, default models and per-agent Vault secrets with the penguin CLI |
+| | `agenthub-models` | Call model APIs through `@prismshadow/agenthub`: streaming text, image generation, speech synthesis and embeddings |
+| Agent Tuning | `agent-creation` | Turn a user requirement into a concrete agent: write the target agent's AGENTS.md and install the skills it needs |
 | | `benchmark-design` | Design and calibrate a multi-Case capability Benchmark with repeated independent evaluations and a traceable baseline |
 | | `agent-evaluation` | Run and score exactly one Benchmark Case run, with CLI execution, Trace provenance checks and private Rubric isolation |
 | | `agent-optimization` | Improve an Agent State from direct feedback or versioned multi-Case Benchmark scores and score-linked Traces |
-| Data Analysis | `data-analysis` | Complete data-analysis tasks with bounded evidence inspection, explicit answer-changing decisions, native artifact handling and final output verification |
-| Penguin Development | `penguin-sdk` | Build AI apps on the SDK (the createSession/run streaming loop) |
-| | `penguin-cli` | Manage model API keys, default models and per-agent Vault secrets with the penguin CLI |
-| | `agenthub-models` | Call model APIs through `@prismshadow/agenthub`: streaming text, image generation, speech synthesis and embeddings |
-| Web Development | `web-design` | Default visual language for generated web pages: minimal black-white-gray |
-| Software Engineering | `software-engineering` | Complete software-engineering tasks: investigate and review code, implement fixes, features and refactors with minimal scope, validate changes, and report verified outcomes |
 
 ## Writing and optimizing Skills