Resolve #1661: Reduce runtime peer internals

[ayden94]

Summary

Closes #1661.

• Reduces @fluojs/runtime direct coupling to peer package internal subpaths by isolating the remaining @fluojs/core/internal and @fluojs/http/internal usage behind runtime-owned seams.
• Preserves runtime public behavior and package export maps while adding regression coverage that keeps peer-internal imports centralized.

Changes

• Added runtime-owned internal wrappers for core metadata reads/writes and HTTP runtime-only helpers.
• Updated runtime bootstrap, module graph, diagnostics, web dispatch, and tests to consume those wrappers instead of importing peer internals directly.
• Added internal-peer-dependencies.test.ts to ensure only the runtime seam files import peer internal subpaths.
• Added a patch changeset for @fluojs/runtime because the public package artifact changes while behavior remains preserved.

Testing

• pnpm install --frozen-lockfile
• pnpm build
• pnpm --dir packages/runtime typecheck
• pnpm --dir packages/runtime build
• pnpm --dir packages/runtime test
• pnpm lint (completed; existing Biome warnings remain in unrelated packages/config/packages/core files while verify:public-export-tsdoc passed)
• LSP diagnostics: clean for changed runtime source/test files

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.

No public runtime API or export-map surface changed; new exported symbols are runtime-internal source seams and are not re-exported from package entrypoints.

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.

This is a contract-preserving refactor. Runtime README behavior and documented runtime invariants are unchanged.

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 package README conformance claims changed.