feat(cli): add OpenCode-compatible workspace references

[limityan]

Summary

• Add OpenCode-compatible @ workspace file and directory completion to the interactive TUI, including #start[-end] file ranges, Enter selection, Tab directory drill-down, arrow/Ctrl-P/Ctrl-N navigation, and Esc dismissal.
• Carry selected paths as typed turn metadata through Embedded and Shared Agent Runtime paths, while Core remains authoritative for Session binding, path kind, source range, persistence, and history recovery.
• Preserve structured references across draft history, failed submission, undo, and fork-prefill flows.
• Map the new optional Runtime capability through the existing SDK Host capability_unavailable error contract so exhaustive consumers remain build-safe.

Architecture and scope

The production path is TUI composer -> CLI runtime client -> AgentWorkspaceReferencePort -> ConversationCoordinator -> services-core path resolver. Shared TUI uses two current-controller, read-only IPC v10 operations; Embedded TUI calls the same typed Runtime port directly.

Core validates normalized workspace-relative paths, rejects symlink/reparse escapes and control-character filenames, verifies Unicode character ranges and token boundaries, then emits an untrusted JSON reminder instructing the agent to use the existing Read/Glob tools. File contents are not read eagerly, so existing permission, cancellation, and audit behavior remains intact.

This PR intentionally does not add a slash command, background index, eager file loading, remote-workspace fallback, Relay behavior, agent/MCP mentions, or a generic public wire protocol. Remote workspace search returns an explicit unavailable result.

Compatibility

The entry and keyboard behavior follows OpenCode's current TUI autocomplete model to avoid introducing a BitFun-specific command or interaction. The existing slash-command routing is unchanged.

Validation

• node scripts/core-boundaries/self-test.mjs
• node scripts/check-core-boundaries.mjs
• cargo test --locked -p bitfun-sdk-host -p bitfun-sdk-host-app — library, protocol, lifecycle, standalone process, and stdio suites passed
• cargo test --locked -q -p bitfun-cli — 507 unit tests plus all CLI integration targets passed
• cargo test --locked -q -p bitfun-core — 1720 passed, 1 ignored, plus integration targets passed
• cargo test --locked -q -p bitfun-agent-runtime -p bitfun-agent-runtime-ipc -p bitfun-runtime-ports -p bitfun-services-core
• cargo check --locked --workspace --exclude bitfun-desktop
• Focused Unicode source-range, invalid path/control-character, workspace resolver, Runtime port, IPC protocol, TUI reference, and SDK Host error-contract tests
• git diff --check
• GitHub CI run 30648782583 — all seven jobs passed on the updated head

A local full cargo check --locked --workspace reached the desktop build script but could not continue because this worktree has no generated src/mobile-web/dist and no frontend node_modules. The equivalent GitHub Rust build jobs remain the authoritative cross-platform full-workspace check.

Review notes

The original isolated adversarial review found and closed four P2 issues before submission: IPC closed-set drift, editable token-boundary drift, control-character reminder injection, and fail-open undo metadata recovery.

After the CI failure, all failed jobs were traced to one exhaustive SDK Host match that omitted MissingWorkspaceReferencePort. The fix adds the existing capability-unavailable mapping and a regression test. A fresh isolated full-PR review then rechecked the TUI entry behavior, Runtime/Core/IPC ownership, remote fail-closed behavior, path safety, persistence, undo/fork recovery, and all RuntimeError consumers; it found no remaining P1/P2 blocker.