🦜 refactor: Use path for Read/Write/Edit/Create File Tools (#13834)

* fix(agents): use `path` for read/write/edit/create file tools

Pairs with @librechat/agents renaming the read_file/write_file/edit_file tool
parameter from `file_path` to `path` (models — esp. Kimi K2 — emit `path` far
more reliably, and it matches grep/glob/list_directory which already use `path`).

- tools.ts: LibreChat's own code/skill file-tool schemas use `path`
  (the skill read_file tool inherits the SDK definition, which is already renamed)
- handlers.ts: read `args.path` for the model-facing tool arg + error messages
- the internal host `readSandboxFile`/`writeSandboxFile` contract is unchanged
- tests updated

Requires @librechat/agents with the param rename (danny-avila/agents#250). All
agents unit suites green (175).

* chore: update @librechat/agents to v3.2.41 and bump related dependencies in package-lock.json and package.json files

* fix(api): Refactor header merging in MCPConnection to use Object.assign for clarity

* test(e2e): mock emits `path` for create/edit file-authoring tools

The mock LLM still sent `file_path` for the create_file/edit_file calls, which the
renamed handlers no longer read -> the skill-file-authoring e2e failed with
'Expected skill to be persisted'. Switch the fixture to `path` to match the tools.
(The internal readSandboxFile/writeSandboxFile contract stays on `file_path`, so
api/server/services/Files/Code/process.js and its spec are unchanged.)

packages/api/package.json

@@ -113,7 +113,7 @@
     "@azure/storage-blob": "^12.30.0",
     "@google/genai": "^2.8.0",
     "@keyv/redis": "^4.3.3",
-    "@librechat/agents": "^3.2.38",
+    "@librechat/agents": "^3.2.41",
     "@librechat/data-schemas": "*",
     "@modelcontextprotocol/sdk": "^1.29.0",
     "@opentelemetry/api": "^1.9.0",