fix(docs-sync): exclude double-extension .*.md files from docs copy

[toiroakr]

Summary

• Add a filter to `fs.cpSync` in `scripts/docs-sync/main.ts` to skip files whose basename matches `.[^.]+.md$` (i.e. double-extension files like `*.template.md`)
• Pre-compile the regex as a module-level constant `DOUBLE_EXT_MD` to avoid per-file allocations
• Prevents template source files from the SDK (introduced in fix(deps): update dependency politty to v0.9.2 sdk#1533) from leaking into the published documentation site