refactor(tool-runtime): move remote tool execution helpers

[limityan]

Summary

• Move remote Delete / Read / LS command planning and output parsing helpers into tool-runtime.
• Move remote Glob / Grep command planning, stdout normalization, match counting, and result windowing helpers into tool-runtime.
• Simplify the core tool adapters so they keep path resolution, workspace shell execution, checkpoint/UI side effects, and ToolResult wrapping only.
• Update the active core decomposition plan and completed summary for the M2 IO/search execution-helper boundary.

Behavior and risk

• No tool schema, permission default, checkpoint, remote fallback, shell cwd, terminal prewarm, or PTY lifecycle behavior changes.
• terminal-core remains the terminal lifecycle owner; agent-tools remains the manifest / admission / GetToolSpec contract owner.
• No Cargo dependency changes.

Verification

• cargo test -p tool-runtime
• cargo test -p bitfun-core grep_tool -- --nocapture
• cargo test -p bitfun-agent-tools
• cargo check --workspace
• pnpm run check:repo-hygiene
• node scripts/check-core-boundaries.mjs

Refs #970