docs: fix dx debug-symbols/keep-names flag syntax

#26 in Riparion/riparion-retro — merged 2026-06-11

What

Corrects the dx build flags added in #25 from --debug-symbols false --keep-names true to --debug-symbols=false --keep-names.

Why

dx 0.7.9 rejects the old form — --debug-symbols takes an =value and --keep-names is a bare boolean flag, so true is parsed as a subcommand:

error: unrecognized subcommand 'true'

Caught when an oregon-trail rebuild failed on the registry builder. The corrected form builds clean (verified: oregon-trail rebuilt with wasm-opt actually running — no more SIGABRT — and shipped to prod).

Scope

Docs + justfile only — no crate source changed, no version bump. Matching fix for the generator template is a separate riparion-cms PR.

🤖 Generated with Claude Code