Introduces FileCache (OrderedDict LRU, st_mtime_ns validation) to avoid
redundant disk reads and duplicate content in conversation context.
Read tools return a short "[Cached]" message on cache hit instead of
resending unchanged file content, saving tokens. Write/edit/delete tools
invalidate affected paths; str_replace pre-warms the cache after edits.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Implement 6 new agent tools — write_file, make_dir, delete_file,
str_replace, patch_apply, run_command — bringing the agent from
read-only observer to active code modifier. All write/shell operations
are gated through the existing permissions service.
Also fix a bug where qwen3.5 thinking mode produces reasoning tokens
but no content after tool results, causing the agent to silently exit.
The loop now detects reasoning-only responses, retries twice, then
injects a nudge message to break the model out of its thinking loop.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
