feat(pxpipe): PXPIPE token saver — multimodal prompt compression (#2465)

Add pxpipe as an experimental fifth Token Saver: Claude-format request
bodies above a configurable size threshold are rendered as dense PNGs
via the pxpipe-proxy library API (transformAnthropicMessages) before
dispatch, cutting estimated input tokens by ~35-60% on token-dense
contexts. Integration follows the Headroom pattern: applied to the final
body in chatCore just before dispatch, fail-open on any error/timeout.

Managed npm install into DATA_DIR/pxpipe, dynamic loader with per-version
cache-bust, JSONL event log with rotation, /api/pxpipe/* endpoints, Token
Saver card (marked experimental) + /dashboard/pxpipe page, and per-request
Activated/Skipped annotation in Request Details. Disabled by default.

src/lib/db/repos/requestDetailsRepo.js

@@ -98,6 +98,7 @@ async function flushToDatabase() {
             providerRequest: truncateField(item.providerRequest, config.maxJsonSize),
             providerResponse: truncateField(item.providerResponse, config.maxJsonSize),
             response: truncateField(item.response, config.maxJsonSize),
+            pxpipe: item.pxpipe || undefined,
           };
 
           db.run(

src/lib/db/repos/settingsRepo.js

@@ -42,6 +42,10 @@ const DEFAULT_SETTINGS = {
   cavemanLevel: "full",
   ponytailEnabled: false,
   ponytailLevel: "full",
+  pxpipeEnabled: false,
+  pxpipeAutoInstall: true,
+  pxpipeMinChars: 25000,
+  pxpipeTimeoutMs: 15000,
 };
 
 async function readRaw() {