fix(hub): close seven bugs found in the refactor review

The PermissionRequest hook posted asks cut to the hub's field limits, so a signature covered less than Claude Code would run; it now posts nothing it cannot sign in full and leaves the decision to Claude Code with a reason on stderr. fields.seconds names the field the caller used in its error. Serving a stored page maps an OSError to 500 instead of a dropped connection. The natural-language line marks the register as seen before it builds the inbox, like the page does. do_POST runs every header guard (host, origin, client, content type, MCP) before it reads the body, so a refused request never costs its upload. The runner's reader closes stdout at EOF, because a close from the executing thread blocked on the buffer lock and could SIGPIPE a command still running. The page title counts only inbox items that are not snoozed.

Committed on the operator's word despite the gate: cost and time are estimates under 98 % other load and include eight new test cases.

🎯 Fix: 88 %
💥 Break: 3 %
💸 Cost: 106 %
⏱️ Time: 113 %
🛡️ Security: 100 %
🏆 Score: 71
🚦 Gate: ⛔ fix 88 % < 90; cost 106 % > 100, time 113 % > 100: ask the operator before the commit

```
/home/kevinveenbirkenbach/Repositories/github.com/kevinveenbirkenbach/skills/.worktrees/feature/kvb-hub
```

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

hub/kvb_hub/fields.py

@@ -59,9 +59,10 @@ def message_text(arguments: dict, name: str) -> str:
     return value.strip()
 
 
-def seconds(value: object, cap: float) -> float:
+def seconds(arguments: dict, name: str, cap: float) -> float:
+    value = arguments[name]
     if isinstance(value, bool) or not isinstance(value, int | float) or not 0 <= value < math.inf:
-        raise ToolError("timeout_seconds must be a finite number of seconds, 0 or more")
+        raise ToolError(f"{name} must be a finite number of seconds, 0 or more")
     return float(min(value, cap))