feat(vault-tui): tui.vim — vim jump motions

[UnbreakableMJ]

What

Opt-in tui.vim (the last tracked config key). On top of the default hjkl
navigation, the browser gains the vim jump motions:

• gg → top, G → bottom
• Ctrl-d / Ctrl-u → half-page (a fixed step — the pure-render App has no
  viewport height)

Because g becomes the gg prefix in vim mode, the generator overlay moves
from g to Ctrl-g while vim mode is on. Non-vim mode is unchanged (g
opens the generator). Decided with the user.

How

• vault-config: [tui] table + tui.vim (bool) — a TUI-only preference,
  read by vault-tui directly (not relayed to the agent), mirroring
  ui.reduced_motion.
• vault-tui: App.vim + a pending_g gg-prefix flag; new focus-aware
  motions move_top/move_bottom/page_up/page_down reusing the existing
  move_* re-masking pattern. handle_normal_key intercepts the vim keys
  before the normal match (which matches g/u/d without checking
  modifiers, so Ctrl-d/Ctrl-u would otherwise alias delete/copy-username).
  load_app sets app.vim from config.

This completes the PRD §7.1 config registry.

Tests

• vault-config: tui.vim round-trip / rejects non-boolean / asserted never an
  agent flag.
• vault-tui: move_top/move_bottom land on first/last, page_* clamp to
  bounds, move_bottom on an empty list is a no-op, and the gg prefix
  arms-once-then-fires.

Local CI-exact gates all green: fmt, fresh isolated clippy -D warnings
(the new App bools needed a reasoned #[expect(struct_excessive_bools)] —
they're independent toggles, not a state enum), cargo test --workspace --all-targets under RUSTFLAGS=-D warnings, cargo deny check (no new deps),
both headless builds.

🤖 Generated with Claude Code