fix(chat): drop forward-looking version labels + add /exit to alwaysAvailable

Two follow-ups from code review on this branch:

1. Drop forward-looking Scarf version labels per the
   `feedback_no_version_bumps.md` rule (release notes own version
   labels, not in-code comments). "Added v2.8 alongside Hermes v0.13."
   becomes "Introduced alongside Hermes v0.13." on
   `HermesSlashCommand.Source.alwaysAvailable`. The `reset()`
   explanatory block in `RichChatViewModel` drops the two "v2.8.0"
   references — the rationale is unchanged, just stops marking the
   change with a Scarf-side version it might never ship under.

2. Add `/exit` to the active-session-only fallback set so the
   implementation matches the doc comment. The doc listed eight
   commands (`/clear`, `/compact`, `/cost`, `/model`, `/tools`,
   `/reload-skills`, `/help`, `/exit`) but only seven were appended.
   Adding `/exit` is the right call since it's a real Hermes ACP
   command; users typing `/exit` on a resumed session will now
   discover and dispatch it before the ACP-advertised version arrives.

Tests: M9SlashCommandTests 30/30 green, Mac scheme builds clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scarf/Packages/ScarfCore/Sources/ScarfCore/Models/HermesSlashCommand.swift

@@ -30,7 +30,7 @@ public struct HermesSlashCommand: Identifiable, Sendable, Equatable {
         /// menu offer discoverable affordances like `/new` even before
         /// the user has opened a session. Once a session starts, the
         /// ACP-advertised version takes over (deduped by name in
-        /// `availableCommands`). Added v2.8 alongside Hermes v0.13.
+        /// `availableCommands`). Introduced alongside Hermes v0.13.
         case alwaysAvailable
     }
 

scarf/Packages/ScarfCore/Sources/ScarfCore/ViewModels/RichChatViewModel.swift

@@ -361,6 +361,12 @@ public final class RichChatViewModel {
                 description: "Show available commands",
                 argumentHint: nil,
                 source: .alwaysAvailable
+            ),
+            HermesSlashCommand(
+                name: "exit",
+                description: "End the current session",
+                argumentHint: nil,
+                source: .alwaysAvailable
             )
         ])
         return result
@@ -710,8 +716,8 @@ public final class RichChatViewModel {
         // `session/new`); they don't change when the user switches
         // sessions. Hermes does not re-emit on `session/load`, so if
         // we wipe here, resumed sessions land at a 4-command fallback
-        // until the user starts a fresh session — exactly the dogfood
+        // until the user starts a fresh session — observed during
-        // bug surfaced during v2.8.0 testing. The caller paths
+        // dogfooding against a Hermes v0.13 host. The caller paths
         // (startNewSession, resumeSession, continueLastSession) all
         // spawn a fresh ACP subprocess; if that subprocess emits a
         // fresh list, our value is replaced; if it doesn't, we keep
@@ -719,7 +725,7 @@ public final class RichChatViewModel {
         // accurate as long as the agent identity hasn't changed. The
         // host-switch case (Local → SSH) tears down the whole
         // ContextBoundRoot so this stale carry-over isn't reachable
-        // there. See WS-2 / v2.8.0 dogfood report.
+        // there.
         projectScopedCommands = []
         currentTurnStart = nil
         turnDurations = [:]