refactor(runtime): centralize service agent adapters

[limityan]

Summary

• Move concrete remote dialog/cancel/file/tracker adapter bindings from remote_server into service_agent_runtime.
• Keep remote-connect command routing, scheduler/session restore/terminal execution, workspace service reads, and remote-SSH runtime core-owned.
• Tighten boundary checks and docs so later HR-C work does not drift into unreviewed runtime owner migration.

Validation

• node scripts/check-core-boundaries.mjs
• $env:BITFUN_BOUNDARY_CHECK_SELF_TEST='1'; node scripts/check-core-boundaries.mjs
• cargo check -p bitfun-core --features product-full
• cargo test -p bitfun-core core_service_agent_runtime_owner -- --nocapture
• cargo test -p bitfun-core remote_execution_prefers_unified_image_contexts_over_legacy_images -- --nocapture
• cargo test -p bitfun-services-integrations --features remote-connect
• git diff --check
• cargo check --workspace
• cargo test --workspace

Risk Review

• No product behavior or feature matrix changes are intended.
• Concrete scheduler/session restore/terminal pre-warm execution remains in core; this PR only changes the adapter ownership file.
• Remote-connect wire/tracker/dialog/file contracts remain owned by services-integrations, and the existing focused contract tests still pass.

Notes

• cargo check --workspace and cargo test --workspace still report the existing bitfun-desktop dead-code warning for parse_clipboard_path_segments; this PR does not touch that file.