feat: session quick switch (Alt+1-9) and pinning

[badchars]

Summary

Add the ability to pin sessions and quickly switch between them using Alt+1 through Alt+9 keyboard shortcuts — similar to browser tab switching. Ported from upstream's session.quick_switch system.

Features

Session Pinning

• Pin/unpin sessions from the /sessions dialog
• Pinned sessions appear at the top of the session list under a "Pinned" category
• Pin state persists across restarts (stored in ~/.local/share/cyberstrike/session.json)

Quick Switch (Alt+1-9)

• First 9 pinned sessions get slot numbers 1-9
• Alt+1 switches to slot 1, Alt+2 to slot 2, etc.
• Slot numbers shown in the session list gutter
• Works from anywhere in the TUI — no need to open session list first

Implementation plan

1. local.tsx — Session namespace

Add session namespace to useLocal with the same persist pattern as model:

• session.pinned() — returns pinned session IDs
• session.slots() — returns first 9 pinned IDs (slot 1-9)
• session.togglePin(id) — pin/unpin a session
• Persists to ~/.local/share/cyberstrike/session.json

2. keybind.tsx — Quick switch keybinds

Add 9 keybind definitions:

session_quick_switch_1: [{ key: "1", alt: true }]
...
session_quick_switch_9: [{ key: "9", alt: true }]

3. dialog-session-list.tsx — UI integration

• Pinned sessions grouped under "Pinned" category at top
• Slot numbers (1-9) shown in gutter
• Pin/unpin keybind in dialog (e.g. ctrl+p)

4. routes/session/index.tsx — Keyboard handler

• Listen for Alt+1-9 globally
• Navigate to local.session.slots()[N-1] on match

References

• Upstream: packages/tui/src/component/dialog-session-list.tsx — local.session.pinned(), local.session.slots(), slotByID gutter rendering
• Upstream: useCommandShortcut("session.quick_switch.1") through session.quick_switch.9

[badchars]

Implemented session quick switch (Alt+1-9) and pinning:

• <leader>p to pin/unpin sessions (up to 9 slots)
• Alt+1 through Alt+9 to instantly switch to pinned sessions
• Pinned sessions appear at top of session list dialog with slot numbers
• /pin slash command for quick access
• Pinned state persisted to ~/.config/cyberstrike/session.json

Commits: c0ff756, 04c4df8, d83156e, 5b6d1b9