feat(keybindings): add resolved action-based keymap

[srothgan]

Summary

add a resolved action-based keymap layer for chat input, autocomplete, and inline prompts, then route the existing interaction handlers through that shared action model.

Keymap architecture

• add src/app/keymap with typed key specs, key contexts, action descriptors, default binding groups, platform validation, and conflict detection
• initialize a resolved default keymap on app startup and use it as the dispatch source for chat, autocomplete, permission, and question contexts
• expose resolved bindings to help rendering so shortcut hints come from the active keymap instead of hardcoded UI text

Interaction handling

• replace raw permission and question key adapters with action executors for inline prompts
• keep permission and plan approval prompts focused on option navigation plus confirm/cancel actions rather than legacy quick-approval shortcuts
• update inline question handling for option movement, multi-select toggles, notes editing, and response annotations through the shared interaction action path

Tool rendering

• let .claude/plans/* markdown plan bodies render at their full wrapped height instead of inheriting the generic tool body cap
• keep normal tool output and non-plan write diffs bounded so large tool results still stay compact
• add regression coverage for long plan markdown rendering and ordinary write-diff capping

Why

Key handling had accumulated separate hardcoded paths across chat input, autocomplete, permissions, plan approvals, and questions. That made shortcut behavior harder to reason about, duplicated help text, and left stale raw-key adapters in place after the inline prompt work moved toward action-based dispatch.

This branch puts key behavior behind a typed resolved keymap so defaults can be validated once, dispatch can ask for an action by context, and help text can describe the same bindings the runtime actually uses. That is the stable base for future configurable keybindings without keeping parallel shortcut implementations alive.

The plan rendering fix addresses a related planning workflow issue: generated .claude/plans/* files are review artifacts, not ordinary noisy tool output. They should render as complete markdown while the generic cap remains in place for normal tool bodies and diffs.

Closes #140

Validation

• Automated:
  • cargo fmt --all -- --check
  • cargo check --offline
  • cargo clippy --all-targets --all-features -- -D warnings
  • cargo test
  • cargo test tool_call::tests::
• Manual: Not run
• Screenshot/video (if UI changed): not captured; keyboard dispatch, help text, inline prompt behavior, and tool rendering are covered by automated tests

Notes

• Breaking changes: default permission and plan approval prompts no longer use legacy raw letter/Ctrl quick-approval shortcuts; they use focused option navigation plus confirm/cancel actions through the resolved keymap
• Docs updated: N/A