Upgrade maintained Go baseline to 1.26

docs/development.md

@@ -10,6 +10,11 @@ polished transcripts and generated artifacts. Start with the
 [Architecture](policy/architecture.md) for normative system boundaries, and the
 [Internal Overview](internal/overview.md) for implemented component ownership.
 
+## Go Prerequisite
+
+Maintained development and verification require Go 1.26. Use the official Go
+1.26 toolchain before running repository commands.
+
 ## What To Read
 
 | When working on | Read | Why |

docs/release.md

@@ -5,6 +5,13 @@ binary release. The synchronous release boundary is a successful push of one
 new tag to `origin`; Woodpecker and Gitea publication happen later and do not
 change that result.
 
+## Go prerequisite
+
+Release preparation requires the maintained Go 1.26 baseline. Tag CI currently
+uses the explicitly pinned `golang:1.26.7` image for candidate validation and
+asset construction; that asynchronous work does not change the tag-push
+completion boundary.
+
 ## Choose a version and write its note
 
 Narratio is past `v1.0.0`. Use an unused stable tag in the exact form

docs/roadmap/implementation.md

@@ -140,7 +140,7 @@ During every stage:
 
 ## Stage 1 — Establish The Go 1.26 Baseline
 
-**Status: Pending**
+**Status: Completed**
 
 ### Goal