fix: resolve file sync infinite bounce loop and unbound local variable bugs

fix: cat() on deleted file returns instantly instead of timing out ...

Root cause: two separate silent-failure bugs caused 15s stalls on file-not-found:

1. agent-node/node.py _push_file(): when a READ arrives for a missing file,
   silently returned without sending any response. The Hub journal sat waiting
   for the full 15s timeout.
   Fix: send ERROR SyncStatus back immediately with task_id so the journal
   resolves at once.

2. ai-hub/assistant.py cat(): after the mirror fast-path found no file, it
   fell through and sent a READ gRPC to the node anyway, compounding the wait.
   Fix: short-circuit with {error: File not found} when the file is absent
   from the session mirror — no node round-trip needed.

test: added Case 9 (TestSmallFileSync) — asserts that cat() on a freshly
deleted file resolves in < 3s on both nodes (guard against regression).

fix(file_sync): check protobuf DESCRIPTOR to correctly detect total_chunks support for fast-path processing

Refactor browser service for parallel worker pool and deep research capabilities. Clean up redundant directories and fix potential path issues for .browser_data.

Fix AI loop stalling and large file sync issues

feat(agent): implement dynamic configuration reloading ...

- The Agent Node now actively reloads its config file during the heartbeat retry loop. \n- Supports both original flat YAML and nested 'cortex' token YAML.\n- Agent no longer caches its node_id or auth_token dynamically at startup, drastically improving resilience on edge.

feat(agent): implement resilient auth handshake loop ...

- The Agent Node will no longer crash and exit if the initial token validation fails or the Orchestrator API is unavailable.\n- Replaced sys.exit(1) on SyncConfiguration rejection with a 5-second sleep and retry loop.\n- This allows nodes to transparently recover once a user dynamically updates their background config with the correct token.

fix(mesh): resolve synology shell bug + bandwidth throttle ...

- Changed mesh-terminal-control to fallback to /bin/sh if bash is missing.\n- Added ~25MB/s bandwidth throttle to Hub/Node file sync to prevent gRPC streaming timeouts.\n- Bumped agent version to 1.0.20.

feat(agent): support FS_ROOT awareness in chat sessions to fix Nas access ...

- Updated Agent to allow out-of-session file access if path is within FS_ROOT.\n- Bumped agent version to 1.0.18.

refactor: organize agent-node client code structure by moving core packages to src/ ...

- Moved agent_node, protos, and shared_core inside src/

- Updated Dockerfile, deployment scripts, compile_protos.sh, installers

- Updated bundle generation in ai-hub to reflect cleaner structure and better README