OpenBPX: äldre versioner att ladda ner

v0.2.1
- Fixes Codex marketplace discovery by using the standard plugins/openbpx plugin layout.
- Documents the current Codex marketplace add/install flow, including refresh steps for older marketplace snapshots.
- Updates BPX CLI, plugin manifests, issue-template examples, installer help examples, and Homebrew formula references to 0.2.1.
- Supported UE version window: FileVersionUE5=1000..1018 (UE 5.0 to UE 5.7).

Changelog
- dc92fd2 chore(sync): promote wilddogjp/wilddog-bpx@794b5046f169e0d19ac968749a62bc1f051cdc8d (main)
- 9b8845d chore(sync): promote wilddogjp/wilddog-bpx@a1e2ff08ea452295cc2af07998ceb11d6856cb9e (main)
- 37e847e chore(sync): promote wilddogjp/wilddog-bpx@a39a027af1f90096e5e67c3da81d38a7b49f75ad (main)
- 507f4e1 chore(sync): promote wilddogjp/wilddog-bpx@e66308ff0108e7946e127da1c7336c84d881a472 (codex/openbpx-marketplace-layout)
- 34171fa chore: sync openbpx marketplace layout
- c08efae chore: sync openbpx source main
- 1508eb3 chore: sync v0.2.1 release prep