feat(cli): support session deletion in Shared TUI

[limityan]

Summary

• add deletion of idle, non-current Sessions to the opt-in Shared TUI deployment
• keep AgentRuntime::delete_session as the only behavior owner: Embedded calls it directly and Shared maps one private local IPC operation to the same request
• reuse the existing TUI Session-operation slot, selector, timeout handling, and outcome_unknown recovery instead of adding a delete task or queue
• centralize the private IPC operation rules for controller checks, idle requirements, Session selection serialization, and timeout semantics
• preserve the declarative-context reload behavior added on main; the combined private protocol is v7

Scope and behavior

• Shared deletion is allowed only when the requesting TUI has no active Turn and the target Session is not current or controlled by another Shared client
• the Session disappears from the selector only after Runtime confirms success
• not_found and session_in_use remain typed failures; a timed-out side effect returns outcome_unknown, closes the connection, and is never retried automatically
• the Shared Host supplies canonical workspace facts; the wire carries only the Session ID
• context reload remains available during an active Turn and affects the next message, matching the behavior already on main
• no public SDK, server endpoint, remote transport, archive/fork/replay/observer capability, general task queue, or second persistence owner is introduced

Rebase notes

Rebased onto gcwing/main@29c2b1569. Both branches had independently used private protocol v6, so the combined delete + reload operation set now uses v7. Conflict resolution retained both user paths and consolidated their policy in one closed operation-rules table.

Validation

• cargo check --workspace
• cargo test -p bitfun-agent-runtime-ipc (43 passed)
• cargo test -p bitfun-cli shared_runtime::tests -- --nocapture (14 passed)
• cargo test -p bitfun-cli session_delete -- --nocapture (4 passed)
• changed Rust files: rustfmt --check
• node scripts/check-core-boundaries.mjs
• pnpm run check:repo-hygiene
• git diff --check gcwing/main...HEAD

The full Windows CLI test binary was also exercised: 469 tests passed and five existing dispatch file-lock/path tests failed outside this diff. Two lock-contention tests are structurally unsupported by the current cfg(not(unix)) implementation, and the remaining failures reproduce as Windows os error 5; this PR does not modify src/apps/cli/src/dispatch.