fix(tools): guard against ValueError on int() env var and header parsing

Three locations perform `int()` conversion on environment variables or
HTTP headers without error handling, causing unhandled `ValueError` crashes
when the values are non-numeric:

1. `send_message_tool.py` — `EMAIL_SMTP_PORT` env var parsed outside the
   try/except block; a non-numeric value crashes `_send_email()` instead
   of returning a user-friendly error.

2. `process_registry.py` — `TERMINAL_TIMEOUT` env var parsed without
   protection; a non-numeric value crashes the `wait()` method.

3. `skills_hub.py` — HTTP `Retry-After` header can contain date strings
   per RFC 7231; `int()` conversion crashes on non-numeric values.

All three now fall back to their default values on `ValueError`/`TypeError`.

tools/process_registry.py

@@ -585,7 +585,10 @@ class ProcessRegistry:
         from tools.ansi_strip import strip_ansi
         from tools.terminal_tool import _interrupt_event
 
-        default_timeout = int(os.getenv("TERMINAL_TIMEOUT", "180"))
+        try:
+            default_timeout = int(os.getenv("TERMINAL_TIMEOUT", "180"))
+        except (ValueError, TypeError):
+            default_timeout = 180
         max_timeout = default_timeout
         requested_timeout = timeout
         timeout_note = None

tools/send_message_tool.py

@@ -689,7 +689,10 @@ async def _send_email(extra, chat_id, message):
     address = extra.get("address") or os.getenv("EMAIL_ADDRESS", "")
     password = os.getenv("EMAIL_PASSWORD", "")
     smtp_host = extra.get("smtp_host") or os.getenv("EMAIL_SMTP_HOST", "")
-    smtp_port = int(os.getenv("EMAIL_SMTP_PORT", "587"))
+    try:
+        smtp_port = int(os.getenv("EMAIL_SMTP_PORT", "587"))
+    except (ValueError, TypeError):
+        smtp_port = 587
 
     if not all([address, password, smtp_host]):
         return {"error": "Email not configured (EMAIL_ADDRESS, EMAIL_PASSWORD, EMAIL_SMTP_HOST required)"}

tools/skills_hub.py

@@ -1788,7 +1788,10 @@ class ClawHubSource(SkillSource):
                     follow_redirects=True,
                 )
                 if resp.status_code == 429:
-                    retry_after = int(resp.headers.get("retry-after", "5"))
+                    try:
+                        retry_after = int(resp.headers.get("retry-after", "5"))
+                    except (ValueError, TypeError):
+                        retry_after = 5
                     retry_after = min(retry_after, 15)  # Cap wait time
                     logger.debug(
                         "ClawHub download rate-limited for %s, retrying in %ds (attempt %d/%d)",