chore: remove unused surfaces (VS Code extension, statusline, landing assets, Docker)

The repo shipped five install/publish surfaces that nothing in the project builds, tests or documents as supported any more. Each one carried its own stale docs, and the Docker/Podman path additionally described a Dockerfile whose COPY of statusline/ would have broken the build the moment that directory went away.

Removed: vscode-extension/ (16 files, marketplace extension for an ID we do not own); statusline/ (3 files, standalone CLI statusline); the repo-root landing/wiki PWA assets (sw.js, manifest.json, robots.txt, sitemap.xml, og-image.svg, favicon.svg, fonts/ - 17 files for pages that no longer exist); .superpowers/ (4 files of scratch brainstorm state, already covered by .gitignore:55); and the container publish path (Dockerfile, docker-compose.yml, .dockerignore, 5 Makefile targets, 2 npm scripts).

Kept deliberately - these are about the USER's containers, not ours: scripts/install-hooks.js container detection and AGENTHUB_ALLOW_CONTAINER_HOOKS (issue #193), server/lib/lane-detect.js docker-compose service detection, server/data/profile-templates/postgres-compose/, server/lib/stage-detect.js 'docker push' detection, the host.docker.internal Prometheus notes, the Config Explorer's reads of the user's own ~/.claude/statusline.py, and .devcontainer/ (its docker-in-docker feature is dropped since it existed only to build the removed Dockerfile).

Docs follow the code: ARCHITECTURE.md loses the VS Code, statusline and container sections plus two dead TOC anchors, and its PWA section is rewritten from three PWAs to one; INSTALL.md, SETUP.md, docs/DEPLOYMENT.md, server/README.md, client/README.md, docs/README.md, docs/HOOKS.md and docs/DATABASE.md drop the same. The Makefile target count in ARCHITECTURE.md is corrected 25 -> 17 (it was already stale).

docs/HOOKS.md

@@ -578,8 +578,8 @@ function sendToServer(hookType, payload) {
 >    Each server appends its `{port, pid, startedAt, dataDir}` entry on
 >    startup and removes it on a clean shutdown. The handler **prunes any
 >    entry whose PID is no longer alive** and POSTs the hook payload to one
->    port per **unique SQLite data directory** (lowest port wins when Docker
->    and `npm run dev` share `~/.claude/agenthub`).
+>    port per **unique SQLite data directory** (lowest port wins when two
+>    instances share `~/.claude/agenthub`).
 > 3. If neither yields a target, the handler falls back to `4820`.
 >
 > Dashboards with **different** databases (e.g. the packaged desktop app using