chore(deps): drop better-sqlite3 and its desktop packaging support

The SQLite write into OpenCode's database was the only consumer of
better-sqlite3 in the repository. Everything that existed to ship its native
binary went with it:

- the dependency in @openchamber/web and @openchamber/electron
- the afterPack hook staging better_sqlite3.node into app.asar.unpacked
- a dedicated @electron/rebuild pass (onlyModules) and its binary assertion,
  so desktop packaging now runs one native rebuild instead of two
- the bundler external entry and the AppImage required-native-module check

Desktop packaging, the AppImage verification tests, and the extension bundle
were re-validated after a clean reinstall, so no stale module could satisfy a
missed import.

.github/workflows/release.yml

@@ -204,8 +204,8 @@ jobs:
           bun run bundle:main
           # npmRebuild=false in package.json, so electron-builder won't
           # recompile native deps on its own — we must rebuild against the
-          # target Electron ABI before packaging, otherwise better-sqlite3/
-          # node-pty/bun-pty crash on require inside the packaged app.
+          # target Electron ABI before packaging, otherwise node-pty/bun-pty
+          # crash on require inside the packaged app.
           bun run rebuild:native
           bunx electron-builder --mac --${{ matrix.arch }} --publish=never
           bun run verify:opencode-cli:packaged