Make in-app help reflect custom keybindings

[jongio]

As a keyboard-heavy Dispatch user, I want the ? help overlay and short help bar to show my actual configured shortcuts so I do not have to mentally translate defaults after remapping keys in config.json.

flowchart TD
    A[Load config keybindings] --> B[Apply overrides in internal/tui/keys.go]
    B --> C[Render help from effective keyMap]
    C --> D[User sees current shortcuts]

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Problem

internal/tui/keys.go already centralizes default bindings, remappable action names, and applyKeybindingOverrides, but internal/tui/components/help.go renders a hand-crafted static overlay. That overlay omits newer actions such as fullscreen preview, command palette, timeline, compare, tags, alias, open file/directory/ref, and copy resume command, and it cannot reflect custom keybindings values described in docs/keybindings.md and README.

Proposed solution

Refactor the help overlay to consume the effective keyMap.FullHelp() and ShortHelp() data after config overrides are applied, preserving the grouped visual layout in internal/tui/components/help.go. Add grouping labels near keyMap.FullHelp() or an adjacent metadata table so the overlay stays readable, update internal/tui/components/help_test.go and internal/tui/keys_test.go, and refresh README/docs examples if the displayed groups change.

User impact

Custom keybindings become discoverable in the UI, new shortcuts stop being hidden from help, and contributors only need to update one keybinding registry when adding actions.

Acceptance criteria

• The ? overlay displays the effective keys after keybindings overrides are applied.
• The short help bar uses the same effective bindings instead of hard-coded default labels.
• All actions in keybindingEntries are represented in grouped help output or intentionally documented as hidden.
• Tests verify a custom binding appears in the overlay and a newly added binding cannot drift silently from help coverage.
• README or docs/keybindings.md notes that in-app help reflects custom bindings.

Complexity

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