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/channels/relay/channel.rs

@@ -423,6 +423,7 @@ impl Channel for RelayChannel {
             tool_name,
             description,
             parameters,
+            allow_always: _,
         } = status
         else {
             return Ok(());
@@ -794,6 +795,7 @@ mod tests {
                     tool_name: "shell".into(),
                     description: "run command".into(),
                     parameters: serde_json::json!({}),
+                    allow_always: true,
                 },
                 &metadata,
             )
@@ -822,6 +824,7 @@ mod tests {
                     tool_name: "shell".into(),
                     description: "run command".into(),
                     parameters: serde_json::json!({}),
+                    allow_always: true,
                 },
                 &metadata,
             )
@@ -854,6 +857,7 @@ mod tests {
                     tool_name: "shell".into(),
                     description: "run command".into(),
                     parameters: serde_json::json!({}),
+                    allow_always: true,
                 },
                 &metadata,
             )