feat: sticky auth profile rotation + usage headers

docs/concepts/model-failover.md

@@ -48,6 +48,17 @@ If no explicit order is configured, Clawdbot uses a round‑robin order:
 - **Secondary key:** `usageStats.lastUsed` (oldest first, within each type).
 - **Cooldown/disabled profiles** are moved to the end, ordered by soonest expiry.
 
+### Session stickiness (cache-friendly)
+
+Clawdbot **pins the chosen auth profile per session** to keep provider caches warm.
+It does **not** rotate on every request. The pinned profile is reused until:
+- the session is reset (`/new` / `/reset`)
+- a compaction completes (compaction count increments)
+- the profile is in cooldown/disabled
+
+Manual selection via `/model …@<profileId>` sets a **user override** for that session
+and is not auto‑rotated until a new session starts.
+
 ### Why OAuth can “look lost”
 
 If you have both an OAuth profile and an API key profile for the same provider, round‑robin can switch between them across messages unless pinned. To force a single profile:

docs/concepts/usage-tracking.md

@@ -11,7 +11,7 @@ read_when:
 - No estimated costs; only the provider-reported windows.
 
 ## Where it shows up
-- `/status` in chats: emoji‑rich status card with session tokens + estimated cost (API key only) and provider quota windows when available.
+- `/status` in chats: emoji‑rich status card with session tokens + estimated cost (API key only). When OAuth/token profiles exist, the **OAuth/token status block** includes provider usage headers (when available).
 - `/cost on|off` in chats: toggles per‑response usage lines (OAuth shows tokens only).
 - CLI: `clawdbot status --usage` prints a full per-provider breakdown.
 - CLI: `clawdbot channels list` prints the same usage snapshot alongside provider config (use `--no-usage` to skip).