Resolve #1609: Export throttler consume input

[ayden94]

Summary

• Closes [audit][area:request-pipeline] Export documented throttler consume input type (P2) #1609.
• Exports the ThrottlerConsumeInput type from @fluojs/throttler's root surface so custom stores can type the low-level consume contract directly.
• Documents the contract decision in the EN/KO throttler READMEs and records a patch changeset for the public package-surface addition.

Changes

• Added ThrottlerConsumeInput to the root packages/throttler/src/index.ts type exports.
• Expanded source TSDoc for ThrottlerConsumeInput and its fields.
• Added a public entrypoint regression test that imports the low-level consume input type from the root barrel.
• Updated packages/throttler/README.md and packages/throttler/README.ko.md public API overview entries.
• Added .changeset/throttler-consume-input-surface.md as a patch release note for @fluojs/throttler.

Testing

• pnpm install --offline --frozen-lockfile (worktree dependency links only)
• pnpm --filter @fluojs/validation --filter @fluojs/http --filter @fluojs/runtime --filter @fluojs/throttler build
• pnpm --filter @fluojs/throttler typecheck
• pnpm --filter @fluojs/throttler test
• pnpm verify:public-export-tsdoc
• LSP diagnostics: clean for packages/throttler/src

Public export documentation

• Changed public exports include a source-level summary.
• Changed exported functions document matching @param / @returns tags where applicable.
• Source @example blocks and README scenario examples still play complementary roles.

Behavioral contract

• No documented behavioral contracts were removed without migration notes.
• New behavioral contracts are documented in the affected package README.
• Intentional limitations are explicitly stated (not silently removed).
• Runtime invariants are covered by regression tests.

Platform consistency governance (SSOT)

• SSOT English/Korean mirror structure remains synchronized for changed governance docs.
• If platform contract docs changed, companion updates include discoverability/docs index, tooling or CI enforcement, and regression-test evidence.
• Any package README alignment/conformance claims are backed by createPlatformConformanceHarness(...) tests.

No platform contract docs or platform conformance claims changed; the platform checklist is not otherwise applicable.