Bring back the side rail as an optional, toggleable panel

[falkoro]

Per request: the cockpit redesign (#42) removed the sidebar — bring it back, improved, but make it optional with a discoverable hint (don't auto-impose it on users).

What changed

• Side rail restored as the cockpit-styled left column (Machine / Remote / Containers / Links / Unlock) — flat hairlines, monospace, small-caps headers.
• New "Panels" toggle in the top bar (leftmost, with a sidebar icon) — always-visible hint that the rail is optional. Shows/hides it; choice persists per browser (localStorage.sdSidebar). A rotating toolbar tip also calls it out.
• body.sidebar-hidden collapses the rail → shells grid goes full-bleed (the clean cockpit look from Cockpit redesign: exe.dev monospace-minimal, sidebar removed, grid is the hero #42).
• Default = shown on this instance (the rail is important here). Productized/multi-tenant deploys can default it hidden so we don't auto-add it for users — that flip lands with the signup slice (frontend default + future env flag).

How

Pure frontend: core.ts (sidebar icon), prefs.ts (sdSidebar pref + applySidebar/toggleSidebar), events.ts (inject the top-bar button + tip), app.css (rail restored + .sidebar-hidden collapse). Compiled to public/*.js. Reversible.

Verified (live, 1600px)

• Default load → rail shown + Panels button highlighted.
• Click Panels → body.sidebar-hidden, rail display:none, grid full-bleed, sdSidebar=hidden persisted.
• Click again → rail back. Console clean. tsc build green.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Restores the cockpit sidebar as an optional “side rail” that users can show/hide via an always-visible “Panels” toggle in the top bar, persisting the choice in localStorage (sdSidebar) while preserving the full-bleed grid layout when hidden.

Changes:

• Added sdSidebar preference with applySidebar() / toggleSidebar() to persist and apply the sidebar visibility state.
• Injected a new top-bar “Panels” button (with a new sidebar icon) and added a rotating tip calling out the toggle.
• Updated CSS to re-enable the left-rail layout by default and collapse it via body.sidebar-hidden to restore the full-bleed grid.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
public/prefs.js	Adds sidebar visibility pref + apply/toggle functions and applies it during applyPrefs().
public/events.js	Injects the “Panels” toggle button into the top bar and adds a new rotating tip.
public/core.js	Adds the sidebar SVG icon used by the new top-bar button.
public/app.css	Restores optional side-rail styling and implements .sidebar-hidden collapse behavior.
frontend/prefs.ts	TypeScript source for sidebar preference + apply/toggle logic (compiled to public/prefs.js).
frontend/events.ts	TypeScript source for top-bar injection + tip addition (compiled to public/events.js).
frontend/core.ts	TypeScript source for the new sidebar icon (compiled to public/core.js).

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