feat(runtime): exec_actions + get_fragments tools; semantic fragment targets

[joelgwebber]

Stacked on #36 (L1 executor). This is A + B-lite of the exec-actions decomposition (sites-10b3): expose the resumable executor as a real WebMCP fallback, composed over corpus-vocabulary fragments.

A — exec_actions + get_fragments (always-on fallback surface)

Two always-on WebMCP tools register alongside the view-scoped tools:

• get_fragments — lists the action fragments available on the current view, each a pluckable {id, tool, op, label, uses}. Returns the current view's base set (ensure_view filtered); the 1-hop guidance horizon + distance tiering is the follow-up (sites-90dc).
• exec_actions — runs an agent-composed list of fragment references (+ arg overrides) resumably. It expands each ref to its compiled step, runs the L1 executor, and returns the status with the untried tail re-expressed as fragment refs. So raw compiled steps / selectors never cross the tool boundary, and a resume is just a re-call with the returned remaining. On an interruption (unexpected modal, missing field) it stops instead of hanging and reports the reason + observed path + remaining refs + a readable remainingView.

Registration dedups against the shared native registry (getTools()), so the tools appear exactly once even though an Angular/Zone SPA boots the injected bundle in several execution contexts (a per-instance flag can't dedup across them).

B-lite — semantic fragment targets (generator)

The generator now carries each step's corpus-vocabulary target into the IR (Step.target): the source compquery for a query step (FormField[label*="First" i] FieldInput), the destination view name for navigate/goto/waitFor-view (a goto deep link resolves to its view via ViewForURL), the key for keypress. Fragment labels and the executor's tail/interrupt projection render this instead of reconstructing raw locators, so an agent composes and reads in component/view names. It is label/provenance only — the runtime still selects via the compiled query, so the IR firewall holds. Golden IRs and the frozen example plans are re-stamped.

Verification (live on JetBlue, --webmcp)

• 6 tools, 1× each (dedup holds across JB's execution contexts).
• get_fragments returns component-vocabulary labels — click FlightCard[flight_no*="{{flight}}"] FareOption[label*="{{cabin}}"], SortControl, and goto → SelectFlights — no raw selectors/URLs.
• exec_actions runs a fragment-ref list (select_fare.0/.1/.2) to completion (done:true, 3/3); on a bad arg it interrupts cleanly with {interrupt:{at,action,reason,observed.path}, remaining:[refs], remainingView:[…]}.
• 65 runtime unit tests pass (new meta-tools.test.ts covers registration, view-filtered get_fragments, and the interrupt→resume ref tail); generator golden tests pass.

Part of sites-10b3. Follow-up: contextual fragment filtering / 1-hop horizon (sites-90dc).