refactor(runtime): route CLI sessions through SDK

[limityan]

Summary

• Route the CLI primary session client through the assembled Agent Runtime SDK for session lifecycle, transcript, local fork, usage generation, dialog submission/cancellation, and exact turn settlement.
• Add scheduler-owned settlement tracking so exec --output-format stream-json does not publish a successful terminal event before Core settlement and patch output complete.
• Move the stable session-usage DTO contract into bitfun-core-types, while retaining compatibility re-exports for existing Core consumers.

Product and architecture boundaries

• Preserve the TUI /usage seven-field metadata schema, local-command turn persistence, markdown projection, and Peer Host/Core compatibility path.
• Keep Core as the runtime owner/provider; the CLI consumes SDK ports and does not construct a second scheduler, persistence owner, or event owner.
• Support local session fork only. Requests carrying remote identity fail with typed NotAvailable; this PR does not add Remote fork behavior.
• ACP, Desktop, Server/Remote, HarmonyOS, and extension execution capabilities are not expanded by this change.

Reliability changes

• Recover/recreate a session only for structured session NotFound; validation failures such as unknown agents remain InvalidRequest.
• Reject duplicate active/recent turn IDs, use UUID-based remote default turn IDs, and fail closed when exact settlement evidence is unavailable.
• Classify only actual settlement timeouts as SettlementTimedOut; other runtime failures remain SystemError.
• Failed submissions are not recorded as settled, while queued, active, cancelled, and dropped accepted turns retain exact settlement lifecycle coverage.

Validation

• cargo +nightly fmt --all -- --check
• node scripts/check-core-boundaries.mjs
• cargo +nightly check --workspace
• cargo +nightly test -p bitfun-core --lib — 1182 passed, 0 failed, 1 ignored
• cargo +nightly test -p bitfun-cli — 224 unit tests plus ACP, exec protocol, plugin, product assembly, and PTY integration suites passed
• git diff --check

Existing upstream deprecation and CLI daemon dead-code warnings remain unchanged.