docs(voice): clarify client and agent tool boundaries

[bobleer]

Summary

• Document the provider-hosted Voice tool list as a client control-plane surface that is independent from the workspace Agent tool registry.
• Explain that run_bitfun_task delegates a complete intent to a normal agentic session whose tools, plugins/MCP integrations, workspace adapters, and permissions are resolved normally.
• Add an extension checklist covering the Rust provider schema, TypeScript command parser/dispatcher, and focused tests.
• Clarify that the Voice client-context snapshot is context data rather than a tool registry.

Type and Areas

Type:

Docs / code comments

Areas:

Rust speech integration, Web UI realtime voice

Motivation / Impact

Future AI agents can extend BitFun Voice without conflating its client-level commands with workspace Agent tools. The comments make the ownership boundary and correct extension path explicit at the relevant implementation sites.

No runtime behavior changes.

Verification

• pnpm run fmt:rs
• cargo test -p bitfun-services-integrations --no-default-features --features speech-realtime --lib speech::realtime::tests:: — 4 tests passed
• pnpm --dir src/web-ui exec vitest run src/flow_chat/components/voice/voiceTaskBridge.test.ts — 11 tests passed
• pnpm --dir src/web-ui exec eslint src/flow_chat/components/voice/useRealtimeVoiceCall.ts src/flow_chat/components/voice/voiceClientContext.ts src/flow_chat/components/voice/voiceTaskBridge.ts
• git diff --check upstream/1.0.0-explore..HEAD

Reviewer Notes

Comments only; no persisted contracts, runtime behavior, or remote scenario behavior changed. Remote workspace, remote control, Peer Device Mode, and Detached Dispatch were therefore not exercised.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.