fix: use raw context window for auto-compact percentage display (#748)

Problem: After auto-compaction with DeepSeek models (e.g., deepseek-chat),
the status line displayed ~16% remaining until next auto-compact, but users
expected ~30% (since compaction reduces usage to roughly half of the full
128k context).

Root cause: calculateTokenWarningState() used the auto-compaction threshold
(effectiveContextWindow - 13k buffer) as the denominator for percentLeft.
For DeepSeek-chat:
- Raw context: 128,000
- Effective: 119,808 (128k - 8,192 output reservation)
- Threshold: 106,808 (effective - 13k buffer)
At 90k usage:
  - Old: (106,808 - 90k) / 106,808 ≈ 16%
  - Expected: (128,000 - 90k) / 128,000 ≈ 30%

Fix: Change percentLeft calculation to use raw context window from
getContextWindowForModel() as denominator, while keeping threshold-based
warnings/triggers unchanged. This makes the displayed percentage show
remaining capacity relative to the model's full context size.

Impact:
- UI now shows correct % of total context remaining
- Auto-compaction trigger point unchanged (still ~90% of effective window)
- All other threshold calculations unaffected

Testing:
- Manual verification: DeepSeek-chat at 90k tokens shows 30% remaining (was 16%)
- Manual verification: Threshold still triggers at ~106k tokens
- Build succeeds: npm run build
- No breaking changes: Callers only depend on percentLeft for display; threshold logic unchanged

Fixes the user-reported discrepancy for DeepSeek and other OpenAI-compatible models.

src/services/compact/autoCompact.ts

@@ -110,9 +110,14 @@ export function calculateTokenWarningState(
     ? autoCompactThreshold
     : getEffectiveContextWindowSize(model)
 
+  // Use the raw context window (without output reservation) for the percentage
+  // display, so users see remaining context relative to the model's full capacity.
+  // The threshold (which subtracts buffer) should only affect when we warn/compact,
+  // not what percentage we display.
+  const rawContextWindow = getContextWindowForModel(model, getSdkBetas())
   const percentLeft = Math.max(
     0,
-    Math.round(((threshold - tokenUsage) / threshold) * 100),
+    Math.round(((rawContextWindow - tokenUsage) / rawContextWindow) * 100),
   )
 
   const warningThreshold = threshold - WARNING_THRESHOLD_BUFFER_TOKENS