AgentCard --watch: minimal incremental refresh (mtime/size, per-card reload, safe parse)

[iqdoctor]

Summary

Propose a minimal incremental refresh path for --watch on AgentCard roots to avoid full app rebuilds, handle partial writes safely, and update only affected agents.

Scope

Applies to --watch for AgentCard roots.

Proposed behavior

• Detect changes using mtime + size; reload only changed card files.
• If a card fails to parse (empty/partial write), log a warning and skip; retry on next change.
• If a tool file changes, reload only cards that reference that tool file.
• Handle removals by unregistering the agent and updating the available agent list without restarting the session.
• Refresh only affected agent instances (no full app rebuild):
  • instance_scope=shared: swap updated agents in place
  • instance_scope=request/connection: bump registry version so new instances see the update
• UX: emit a short “AgentCards reloaded” line and refresh the available agent list.

Why

• Avoids unnecessary full reloads for small edits
• Prevents crashes on partial writes during save
• Enables smooth REPL workflows (add/modify/delete cards live)

Notes

This is intentionally minimal; deeper dependency/graph handling can follow later.

[iqdoctor]

PR #605

[iqdoctor]

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