fix(cdp): hard Chromium 131 pin blocks all real-URL lints on modern systems

[aram-devdocs]

Found during the e2e test pass for issue #2 / phase 1 / phase 2.

Symptom

plumb lint <real-url> fails immediately with error: Chromium major version <N> is not supported (Plumb pins to 131) whenever the host's Chromium / Chrome major version is anything other than exactly 131.

PINNED_CHROMIUM_MAJOR is defined as 131 (crates/plumb-cdp/src/lib.rs:57) and the gate is an equality check at crates/plumb-cdp/src/lib.rs:501 (if found == PINNED_CHROMIUM_MAJOR).

Chromium 131 is the November 2024 release. On any reasonably current developer machine, this gate refuses to run.

Reproduction

$ ./target/release/plumb lint https://example.com --format json
error: Chromium major version 139 is not supported (Plumb pins to 131)
$ echo $?
2

System binaries available locally:

• Chromium 139.0.7216.0 at /Applications/Chromium.app/Contents/MacOS/Chromium
• Google Chrome 147.0.7727.102 at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

--executable-path points at a different binary but does not bypass the version check. There is no env var, feature flag, or CLI flag that skips it.

Why this matters

Phase 1 acceptance criterion (#10):

`plumb lint https://plumb.aramhammoudeh.com --format json` renders a real page via Chromium and emits ≥1 violation from a real rule.

This criterion cannot be satisfied on any host without a fresh Chromium 131 install — and Chromium 131 is no longer the current download from chromium.org or via Homebrew (brew install --cask chromium ships latest).

Rule-engine / config / format work landed in phases 1+2 (8 rules registered, all integration tests green), but the only path to drive a real page is gated behind a binary that's hard to obtain.

Suggested fix

Pick one (or combine):

1. Bump the pin to whichever Chromium major the project actively supports (e.g. 139 or whatever CI uses).
2. Switch the gate from == to >= with a documented "tested up to" upper bound — every CDP feature plumb uses is stable across recent majors.
3. Add a --skip-chromium-version-check flag (or PLUMB_SKIP_CHROMIUM_VERSION_CHECK=1 env) so users on the latest Chrome can opt in without modifying source. Print a warning that emitted output is unsupported.

Whichever path you take, also fix the misleading install hint at crates/plumb-cdp/src/lib.rs:419 which currently tells users --executable-path is the workaround — it is not.

Parent

Refs #2.