refactor(codemode): name the data boundary and prepare tools once

[rekram1-node]

Summary

Second cleanup pass, following #48009. Behavior-preserving; the existing copyOut parity tests (toStrictEqual) now pin the new functions.

One data boundary module

copyIn(value, label, preserveCodeModeValues) + copyOut(value, mode) did three different jobs behind a boolean and a two-pass pipeline. They're replaced by a new dependency-free data.ts with one walker and three named directions:

Function	Direction	Replaces
toProgram(value, label)	host runtime result → program (keeps Values.*, wraps host Date/Map/…)	boundedData / copyIn(…, true)
fromData(value, label)	host data → program (Date/URL → strings, null-prototype copies)	copyIn(…, false) on tool output and JSON.parse
toData(value, label, undefinedAs?)	program → host JSON in one walk	copyOut(copyIn(…), "json" | "nullify")

Tool arguments and the execution result now traverse once instead of twice. SafeObject, isBlockedMember, and ToolRuntimeError move to data.ts too, so the stdlib and openapi/spec.ts no longer import the tool runtime (Effect Schema, search, hooks) for a three-line blocked-name check.

JSON.stringify is restructured so each branch does exactly one copy instead of a discarded validation pass plus a real one.

Tools prepared once

ToolRuntime.prepare(tools) now returns { root, catalog, searchIndex } and ToolRuntime.make consumes it. Previously the trie was rebuilt on every execution (and twice per one-shot CodeMode.execute). Removed: searchIndex(), DiscoveryPlan, the dead ToolRuntime.root field.

codemode.ts

• Options is the base type; ExecuteOptions = Options & { code } (was inverted via Omit).
• Options extends ToolCallHooks instead of redeclaring both hooks.
• execute = make(options).execute(options.code).
• executeProgram(code, prepared, limits, hooks) is generic in R and no longer takes the public options bag, removing the reverse codemode.ts → execute.ts type coupling.

Net −44 lines.

Test plan

• bun typecheck (with noUnusedLocals)
• bun test — 1141 pass
• packages/core has no references to removed exports