fix(approval): make "always" auto-approve work for credentialed HTTP requests (#1257)

The HTTP tool returned `ApprovalRequirement::Always` for requests with
credentials, but `Always` is hardcoded to ignore the session auto-approve
set. This meant users who clicked "always" were re-prompted on every
subsequent HTTP call — the UI offered "always" but the backend ignored it.

Two fixes:
1. HTTP credentialed requests now return `UnlessAutoApproved` instead of
   `Always`, so the session auto-approve set is respected.
2. `StatusUpdate::ApprovalNeeded` now carries `allow_always: bool`. All
   channel UIs (Telegram, Slack, Signal, REPL, Web) conditionally hide
   the "always" option when a tool truly requires per-invocation approval
   (`ApprovalRequirement::Always`, e.g. destructive shell commands).

Also boxes `PendingApproval` in `AgenticLoopResult::NeedApproval` to fix
a pre-existing clippy `large_enum_variant` warning.

Regression tests included (test_credentialed_requests_respect_auto_approve,
test_allow_always_matches_approval_requirement) but CI heuristic cannot
detect them in cross-fork PR diffs.

[skip-regression-check]

Co-authored-by: Tyler <[email protected]>

src/agent/session.rs

@@ -188,6 +188,15 @@ pub struct PendingApproval {
     /// through the approval flow even if the approval message lacks timezone.
     #[serde(default)]
     pub user_timezone: Option<String>,
+    /// Whether the "always" auto-approve option should be offered to the user.
+    /// `false` when the tool returned `ApprovalRequirement::Always` (e.g.
+    /// destructive shell commands), meaning every invocation must be confirmed.
+    #[serde(default = "default_true")]
+    pub allow_always: bool,
+}
+
+fn default_true() -> bool {
+    true
 }
 
 /// A conversation thread within a session.
@@ -1106,6 +1115,7 @@ mod tests {
             context_messages: vec![ChatMessage::user("do it")],
             deferred_tool_calls: vec![],
             user_timezone: None,
+            allow_always: false,
         };
 
         thread.await_approval(approval);
@@ -1132,6 +1142,7 @@ mod tests {
             context_messages: vec![],
             deferred_tool_calls: vec![],
             user_timezone: None,
+            allow_always: true,
         };
 
         thread.await_approval(approval);