fix(tools): collapse code-mode executor to run_code for model-direct calls

wireSchemas() already advertised only run_code under mode: 'code', but the
executor resolved every call through get(), which returns the full visible
map plus the reserved transport. A model could name a native tool directly
and bypass run_code entirely. Route the execution-path lookups through a
new private resolveExecution() that applies the mode collapse at the
operation boundary: model-direct calls under 'code' may only name run_code
(UNKNOWN_TOOL otherwise), while SDK sub-dispatches (parent token set) keep
every visible tool. get()/schemas() public semantics are unchanged.

The denial happens at createExecution, before the extensible policy
pipeline — pre-execute listeners, approval ask, and guards never observe
a call that is deterministically denied. A collapsed call honors the
pre-dispatch cancellation contract, routes aborted results through the
visible tool's finalizeContent, and captures the finalizer before
argument materialization.

Under code mode, a system-prompt/assemble listener filters out tool:*
guidance sections that told the model to call native tools directly.
The tools:sdk section and SDK types remain so programs can still use
all tools through run_code.

Regenerated docs, catalogs, graphs, scoped events, and re-recorded
translation pairs.

Fixes #1815

docs/subsystems/tools.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write docs/subsystems/tools.md
-tools.md: 54d20de3b4d1f2ff6d03a8e89e9356eef403382a
-tools.zh.md: f8a35ffa7121438b0623f2a0972f90df2923ac89
+tools.md: 4f0360f45e7ed4f3537bedeb0f370f8eb3472ab9
+tools.zh.md: aa6c67c6379e4a9b9ab7bdc473f6294d063e3649