docs: add RSR-PHILOSOPHY.adoc — canonical 'solutions at source' doctrine (#448)

Canonical estate operating-doctrine statement + licence-consistency
script rework (MPL-2.0 code / CC-BY-SA-4.0 prose split) + several CI
reusable-workflow fixes already landed piecemeal (#429-#442) that this
branch was stacked on.

**Left un-armed for auto-merge deliberately** — this declares canonical
estate doctrine and should be owner-ratified before merging, not
auto-merged.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: hyperpolymath