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).

.gitattributes

@@ -13,13 +13,3 @@
 *.ttf binary
 *.eot binary
 *.db binary
-
-# ── GitHub Linguist overrides — keep language stats honest ──────────────────
-# wiki/mermaid.min.js is a vendored, minified third-party library (Mermaid);
-# it is not project source code and must not count toward language stats.
-wiki/mermaid.min.js linguist-vendored
-
-# wiki/i18n-content.js is machine-assembled translation data (see its header:
-# "AUTO-GENERATED wiki body-content translations ... Do not hand-edit").
-# It is a data bundle keyed by English innerHTML, not hand-written JavaScript.
-wiki/i18n-content.js linguist-generated