Add keyboard shortcuts to jump Board / Memory / Portfolio / Advise

[telivity-otaip]

Why

Power users live on the board. Jumping sections with the mouse is slow. Vim-style or g then letter chords fit a local-first ops tool — and make demos snappier.

Size

M — small keydown handler + discoverability.

Proposal

When focus is not in an input/textarea/contenteditable:

Keys	Action
g then b	Board
g then m	Memory
g then p	Portfolio
g then a	Advise

Reuse whatever data-section / tab switching already powers the header tabs (web/ui/board.mjs + web/ui/state.mjs).

Requirements

1. Ignore chords while typing in fields (JD paste, memory body, settings, etc.).
2. Don’t fight Escape (already closes builder/drawer).
3. Add a one-line discoverability hint in Settings or a tiny “Keyboard” note under the header — not a floating badge overlay.
4. Optional: document in web/README.md.

Acceptance

• Shortcuts switch sections when not typing
• Typing in JD / memory / settings never triggers navigation
• Works with both desktop hdr-tabs and doesn’t break mobile tabs
• npm test passes

Out of scope

Full command palette; customizing keybindings; macOS system shortcut conflicts beyond the usual.