feat(m7.3): TypeScript registry + ask/run loop, budgets, stop

[shamspias]

• CapabilityRegistry: the only path to a capability. Validates arguments against the schema BEFORE executing (model output is untrusted — the schema is the prepared statement, §2.6: required keys, JSON types, and additionalProperties all fail closed), then invokes the handler and returns the outcome as data (CapabilityResult); a thrown handler error becomes errors-as-data, never crossing the loop. Unknown names return a closest-match suggestion (Levenshtein). Only a duplicate registration throws.
• runLoop: the async ETCSLV lifecycle (Engage → Think → Call → Sense → Loop? → Verify) — the model is the only stochastic step; dispatch and stopping are deterministic and owned here (§2.14). Returns a RunReport (outcome / output / finish / usage / turn / executed / reason / trace_id).
• The ask/run boundary: ask() is structurally read-only — a write turn is refused before anything executes (write_in_read_only, §2.1). run() may write, but the policy → approval → audit gate lands in M7.4; until then a write fails closed (write_denied, never executed). The caller's principal propagates as a Context into every capability call (§2.7).
• Budget {max_turns, max_tokens} + defaultBudget (8 turns) + StopCondition (GoalReached / MaxTurns / firstStop) — a runaway loop stops deterministically (§2.13).
• Agent: a config-object class (idiomatic TS rather than Go's functional options) with ask()/run(); a duplicate capability name is a control-plane throw.

Verified: make js-check green — format, typecheck, 54 tests (registry register/ list/validate/call, unknown-with-suggestions, handler-throw-as-data; read goal completes; ask refuses + run fails-closed on a write with the handler never invoked; budget stops a runaway loop; Agent trace id + principal propagation + duplicate detection).