fix: point optional-dep install hints at the venv's python (#11938)

Error messages that tell users to install optional extras now use
{sys.executable} -m pip install ... instead of a bare 'pip install
hermes-agent[extra]' string.  Under the curl installer, bare 'pip'
resolves to system pip, which either fails with PEP 668
externally-managed-environment or installs into the wrong Python.

Affects: hermes dashboard, hermes web server startup, mcp_serve,
hermes doctor Bedrock check, CLI voice mode, voice_mode tool runtime
error, Discord voice-channel join failure message.

hermes_cli/doctor.py

@@ -895,8 +895,8 @@ def run_doctor(args):
                 _model_count = len(_br_resp.get("modelSummaries", []))
                 print(f"\r  {color('✓', Colors.GREEN)} {_label} {color(f'({_auth_var}, {_region}, {_model_count} models)', Colors.DIM)}           ")
             except ImportError:
-                print(f"\r  {color('⚠', Colors.YELLOW)} {_label} {color('(boto3 not installed — pip install hermes-agent[bedrock])', Colors.DIM)}           ")
-                issues.append("Install boto3 for Bedrock: pip install hermes-agent[bedrock]")
+                print(f"\r  {color('⚠', Colors.YELLOW)} {_label} {color(f'(boto3 not installed — {sys.executable} -m pip install boto3)', Colors.DIM)}           ")
+                issues.append(f"Install boto3 for Bedrock: {sys.executable} -m pip install boto3")
             except Exception as _e:
                 _err_name = type(_e).__name__
                 print(f"\r  {color('⚠', Colors.YELLOW)} {_label} {color(f'({_err_name}: {_e})', Colors.DIM)}           ")

hermes_cli/main.py

@@ -6029,7 +6029,7 @@ def cmd_dashboard(args):
         import uvicorn  # noqa: F401
     except ImportError:
         print("Web UI dependencies not installed.")
-        print("Install them with:  pip install hermes-agent[web]")
+        print(f"Install them with:  {sys.executable} -m pip install 'fastapi' 'uvicorn[standard]'")
         sys.exit(1)
 
     if not _build_web_ui(PROJECT_ROOT / "web", fatal=True):

hermes_cli/web_server.py

@@ -56,7 +56,7 @@ try:
 except ImportError:
     raise SystemExit(
         "Web UI requires fastapi and uvicorn.\n"
-        "Run 'hermes web' to auto-install, or: pip install hermes-agent[web]"
+        f"Install with: {sys.executable} -m pip install 'fastapi' 'uvicorn[standard]'"
     )
 
 WEB_DIST = Path(__file__).parent / "web_dist"