chore: drop eth_chainId and net_version from PROXY_METHODS (closes #326)

handleRpc answers both methods itself before it reaches its proxy branch, so
the two list entries were never used and the list named two methods that are
never sent to the RPC endpoint. No other entry is answered earlier.

PROXY_METHODS is now exported from the background script so that
tests/proxyMethods.test.js can send every listed method from a page and fail
on any that does not reach the RPC endpoint.

Model: opus-5-5

TODO.md

@@ -45,6 +45,14 @@ but the review is broader than any of them.
 
 # Completed Steps
 
+- 2026-10-05: `PROXY_METHODS` in `src/background/index.js` no longer lists
+  `eth_chainId` and `net_version`
+  ([#326](https://git.eeqj.de/sneak/AutistMask/issues/326)). `handleRpc` answers
+  both itself before its proxy branch, so the list named two methods that are
+  never sent to the RPC endpoint. No other entry is answered earlier.
+  `tests/proxyMethods.test.js` sends every listed method from a page and fails
+  on any that does not reach the RPC endpoint.
+
 - 2026-10-05: The popup's Content Security Policy no longer allows inline style
   ([#328](https://git.eeqj.de/sneak/AutistMask/issues/328)): `style-src` is
   `'self'` in both manifests, pinned in `tests/manifest.test.js`. The 42