refactor(core): move feature seed and session state owners

[limityan]

Summary

• Move built-in MiniApp seed orchestration into product-domain host contracts; keep core as the concrete IO/recompile adapter and preserve the legacy core entrypoint.
• Move SessionStateManager into bitfun-agent-runtime; keep the old core path as a compatibility re-export and add boundary guards against owner backflow.
• Align the bundled PPT Live MiniApp registered version with its bundled metadata, and move MCP result-rendering test coverage to the services-integrations owner path.
• Update the core decomposition plan/completed notes to reflect the completed owner migrations and remaining large PR scope.

Risk / behavior

• Intended as behavior-preserving owner migration. Seed skip, local-override preservation, update-record handling, marker writes, recompile path, session state transitions, and SessionStateChanged event shape are covered by focused tests.
• bitfun-product-domains --no-default-features remains lightweight; MiniApp seed orchestration is behind the existing MiniApp feature path.
• The PPT Live version now reports the bundled version already declared by its asset metadata.

Verification

• pnpm run fmt:rs
• cargo test -p bitfun-product-domains --no-default-features
• cargo test -p bitfun-product-domains --features product-full
• cargo test -p bitfun-agent-runtime
• cargo test -p bitfun-core --features product-full miniapp::builtin
• cargo test -p bitfun-services-integrations --features mcp --lib mcp_tool_result_rendering_does_not_pretruncate_before_storage_policy
• cargo check -p bitfun-core --no-default-features
• cargo check -p bitfun-core --features product-full
• cargo check --workspace --exclude bitfun-desktop
• node scripts/check-core-boundaries.mjs
• node --test scripts/check-core-boundaries.test.mjs
• pnpm run check:repo-hygiene
• git diff --check

Note: full cargo check --workspace was also attempted after the rebase, but the local isolated worktree lacks src/mobile-web/dist, so the desktop build script stopped before compiling bitfun-desktop.