v0.1.0-alpha.58

feat: parallel tool execution + dead code cleanup (alpha.58)

The infrastructure was already parallel-capable: edge fans out tools via
Promise.all, qlaud-client's onToolDispatchStart is intentionally fire-and-
forget so concurrent tool_use blocks run their executeTool + safeSubmit
in parallel. The model just wasn't being told to batch.

- qcode-system-prompt.ts (edge): explicit "run independent tools in parallel"
  guidance. Examples: 4 reads in one message, grep+glob in one message,
  2 task subagents in one message. Reads are always safe to batch; writes/
  bash default to sequential.
- qlaud-client.ts: comment locks in the fire-and-forget invariant so future
  edits don't accidentally serialize the SSE event loop behind a single
  tool's executeTool.
- agent.ts: delete legacy runAgent (~160 lines). Dead since Sprint C-2;
  ChatSurface only uses runThreadAgent. Drops MAX_LOOPS, streamMessage
  import, RunAgentOpts type. Keeps SYSTEM_PROMPT_AGENT/PLAN local copies
  as the qlaud-runtime fallback.