Implement tool approval, fix tool definition refresh, and wire embeddings

This commit addresses three critical issues from code review:

1. Tool approval enforcement: Tools declaring requires_approval() (shell,
   http, file write/patch, build_software) now gate execution. Adds
   PendingApproval struct, session-scoped auto-approved tools set, and
   approval flow with yes/no/always commands.

2. Tool definition refresh: Tool definitions now refresh each iteration
   in both chat and job loops, so newly built tools become visible
   immediately within the same session.

3. Worker tool call handling: Changed respond() to respond_with_tools()
   when select_tools returns empty, properly executing tool calls instead
   of formatting them as text.

Also includes prior work from the plan:
- Wire embeddings provider (OpenAI + NEAR AI) to workspace
- Load workspace system prompt (identity files) into LLM context
- Route heartbeat notifications through channel manager
- Enable auto-context compaction when threshold exceeded
- Refactor to config structs (AgentDeps, WorkerDeps, LlmCallRecord)
- Fix clippy warnings (saturating_sub, too_many_arguments)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

src/workspace/mod.rs

@@ -48,7 +48,7 @@ mod search;
 
 pub use chunker::{ChunkConfig, chunk_document};
 pub use document::{MemoryChunk, MemoryDocument, WorkspaceEntry, paths};
-pub use embeddings::{EmbeddingProvider, MockEmbeddings, OpenAiEmbeddings};
+pub use embeddings::{EmbeddingProvider, MockEmbeddings, NearAiEmbeddings, OpenAiEmbeddings};
 pub use repository::Repository;
 pub use search::{SearchConfig, SearchResult};