refactor(remote-connect): move runtime policy helpers

[limityan]

Summary

• move remote-connect pure policy helpers into bitfun-services-integrations: legacy image fallback/preference, restore-target decision, cancel decision, and remote file-transfer size/chunk/name policy
• keep core-owned runtime behavior in place: dispatcher assembly, ImageContextData adapter, file IO/path resolution, session restore execution, terminal pre-warm, and product submission routing
• add owner-crate contract tests plus boundary checks and update decomposition docs/AGENTS guardrails

Functional Boundary

• No remote command, response, active-turn, cancel, image-context, or file-transfer wire behavior is intentionally changed.
• AgentSubmissionPort still rejects generic attachments; this PR does not implement broader multimodal/runtime migration.
• Core remains responsible for actual remote execution routing, file IO/path resolution, and product runtime assembly.

Validation

• rustfmt --edition 2024 --check src/crates/services-integrations/src/remote_connect.rs src/crates/services-integrations/tests/remote_connect_contracts.rs src/crates/core/src/service/remote_connect/remote_server.rs
• node scripts/check-core-boundaries.mjs
• git diff --check gcwing/main..HEAD
• cargo test -p bitfun-services-integrations --features remote-connect
• cargo test -p bitfun-core remote_ -- --nocapture
• cargo check --workspace (passes with existing CLI unused-import warning in src/apps/cli/src/ui/theme.rs)