Add an Edit page and group the sidebar like it

[rndaom]

What changes

• Edit page. Edit on the Setups page opens one page for the setup in the game. It lists every setting with its current value under Look, Feel, Sound, Mods, Performance and Advanced. Each row opens the pane that changes it. Rows whose pane has unsaved changes show the change dot, and values from cfgs that can't be read say "Can't read" instead of guessing.
• Sidebar. The panes use the same groups: Look (HUD, Crosshair, Viewmodels), Feel (Gameplay, Binds), Sounds / Mods / Performance, Advanced (Files, Launch), then Inventory. An Edit entry under Setups names the setup in the game and returns to the Edit page. The one-pane groups share a group without a heading, because a heading there only repeats the pane's name. With that and slightly tighter spacing, the sidebar fits at 1200×800, even with the TF2-running bar.
• Comfig is now shown as Performance in the sidebar, the pane title, the Files button and the guide. Internal ids and file names stay as they are.

The Edit page only reads. It uses the snapshot the panes already load (profile detail, effective startup cfg values, mastercomfig state, saved launch options), plus get_setup_overviews for the Casual setup count. Nothing the app writes has changed.

Docs: CHANGELOG, docs/guide/profiles.md (new Edit page section), docs/guide/comfig.md and the guide index, docs/ARCHITECTURE.md.

Checks

• pnpm test, pnpm check, tsc --noEmit
• cargo fmt --all --check, cargo clippy --workspace --all-targets -- -D warnings, cargo test --workspace --locked
• Browser preview at 1200×800 and 960×640: ?preview=setups, every ?preview=settings-* state, ?preview=welcome, and the new ?preview=settings-edit