chore: contributor workflow — templates, git-cliff, gitea-workflow doc (closes #31) (#38)

.gitea/ISSUE_TEMPLATE/adr-proposal.md

@@ -0,0 +1,24 @@
+---
+name: ADR proposal
+about: Propose a decision that needs recording before coding (CLAUDE.md §14)
+title: "ADR: "
+labels:
+  - type:adr-proposal
+---
+
+**Decision to be made:**
+
+**Context / forces:** <!-- what makes this non-obvious; constraints, trade-offs -->
+
+**Options considered:**
+1.
+2.
+
+**Proposed option + why:**
+
+**Consequences:** <!-- what becomes easier/harder; what we commit to -->
+
+**Coupling rules touched (CLAUDE.md §8):** <!-- none, or which and why -->
+
+> On acceptance, the ADR file (`docs/architecture/adr-NNNN-title.md`, Nygard
+> template) lands in the PR that implements the decision.