Wires the live-typing half of in-buffer search for the terminal
frontend, on a frontend-agnostic core so the GPU (next commit) can
share it.
EditorCore gains a `search: Option<SearchSession>` (query + origin
cursor + direction) and the `search_*` methods that drive it:
begin records the origin, input_char/backspace re-run `find_all`
against the origin buffer and refocus the match nearest the origin
(failing searches anchor the cursor back at the origin), step walks
the store's active match (wrapping, also usable post-accept), and
finish either keeps the cursor + matches (accept) or restores the
origin and clears them (cancel). The matches live in the shared
`search_store`, so the decorations producer and the TUI SearchView
light up live as you type.
Input routing is intercepted in `EditorState::dispatch_key`: while
a search runs, every key flows through `dispatch_search_key`
(SearchKey::from_chord) instead of the global keymap — printable
chars extend the query, C-s/C-r (and Down/Up) step, RET accepts,
C-g/Esc cancel, BS shortens. This is the same dispatch path the
daemon's `FrontendEvent::Key` round-trip uses, so the daemon-side
search already works; the GPU just needs to route keys + show the
prompt (commit 4). The TUI paints an `I-search: <query> (n/m)`
prompt on the bottom row while keeping the terminal cursor in the
buffer at the active match.
C-s / C-r start the search (search.forward / search.backward Lua
commands → ed.search_start). Both keys were free in the default
map (save is C-x C-s, redo is C-x r), so isearch lands without
disturbing the CUA / Emacs editing keys — no cursor.right rebind
needed (the framing doc had flagged C-f for veto; C-s is cleaner
and Emacs-faithful).
Any edit now marks the buffer's matches stale in apply_active_edit
(M11.8), closing the headline "stale-after-edit linger" bet:
accepted highlights vanish the moment the text they described
changes, rather than painting at wrong offsets.
Tests: EditorCore-level (begin/type/step/wrap/focus-from-origin/
cancel/accept/backspace/smart-case/stale-on-edit) and dispatch-
level acceptance (C-s drives the whole loop; Esc restores; query
keys never self-insert).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>