fix: unicodeEncodeError when UIPATH_PROCESS_KEY contains non-ASCII characters

[cristian-groza]

• Agent or solution names containing non-ASCII characters are included in UIPATH_PROCESS_KEY, which is passed as the X-UiPath-ProcessKey HTTP header to the LLM Gateway
• HTTP headers must be ASCII-only per RFC 7230; httpx enforces this with value.encode("ascii"), causing a UnicodeEncodeError that crashes the agent before it can execute
• Fix: percent-encode the header value with urllib.parse.quote() so non-ASCII chars become ASCII-safe (e.g. 請 → %E8%AB%8B); server side can decode
  e.g.
  [2026-02-26 12:57:56.368] info: UiPath.Executor.CodedAgent.JobExecutors.PythonAgentJobExecutor[0] UIPATH_PROCESS_KEY=Solution.17.agent.GetCompanyIdAgentAgent-請-test