Add dead code analysis (reanalyze) to all ReScript libs

[BlueHotDog]

Problem

Only libs/client has dead code analysis configured. The remaining 11 ReScript libraries have no reanalyze config and no CI checks:

Library	reanalyze in rescript.json	CI job
libs/client	Yes	dead-code-client
libs/bindings	No	No
libs/experimental-rescript-webapi	No	No
libs/frontman-astro-browser	No	No
libs/frontman-astro	No	No
libs/frontman-client	No	No
libs/frontman-core	No	No
libs/frontman-nextjs	No	No
libs/frontman-protocol	No	No
libs/frontman-vite	No	No
libs/logs	No	No
libs/react-statestore	No	No

This gap let withLock in frontman-core ship as dead code — defined in src, only called from tests. Caught during PR #805 review.

What to do

1. Add "reanalyze": { "analysis": ["dce"] } to each library's rescript.json
2. Add CI jobs (or a single matrix job) that runs npx @rescript/tools reanalyze -config for each lib
3. Fix any existing dead code flagged by the initial run
4. Consider using the -transitive flag to catch code only kept alive by test imports

Notes

• The existing dead-code-client job in .github/workflows/ci.yml:374-413 is a good template
• A matrix strategy over all libs would be cleaner than N separate jobs