docs: split CLAUDE.md into linked guides

CLAUDE.md

@@ -11,40 +11,9 @@ Marketplace as **OSSystems Nix Actions**
   `OSSystems/nix-actions/update-flake@v1`. Not separately listed (one
   Marketplace listing per repo).
 
-## Versioning
+## Guides
 
-Two kinds of tags, both on the same release commit:
-
-- `vX.Y.Z` (e.g. `v1.0.0`) — **immutable**. Matches a published Marketplace
-  release; never move it once published.
-- `vX` (e.g. `v1`) — **movable major tag**. Most callers pin `@v1`, so it must
-  be fast-forwarded to each new release on the same major line. `v1` is a *tag*,
-  not a branch.
-
-## Cutting a new release
-
-1. Land all changes on `main`.
-2. Tag the immutable version and push it:
-   ```
-   git tag -a vX.Y.Z -m "vX.Y.Z" && git push origin vX.Y.Z
-   ```
-3. Move the major tag to the same commit:
-   ```
-   git tag -f vX HEAD && git push -f origin vX
-   ```
-4. Create the GitHub release from the `vX.Y.Z` tag
-   (`gh release create vX.Y.Z --title vX.Y.Z --notes ...`). On the **first**
-   release of a major line, also check "Publish this Action to the GitHub
-   Marketplace" in the release UI (the Marketplace checkbox is UI-only) and
-   accept the Developer Agreement.
-
-For a docs/non-release change that should reach `@v1` callers without a new
-version, just move the major tag: `git tag -f v1 HEAD && git push -f origin v1`.
-
-## Marketplace constraints (when editing `action.yml`)
-
-- `name` must be globally unique across all Marketplace actions, users, and
-  orgs — hence the `OSSystems` prefix.
-- `description` must be under 125 characters.
-- `branding.icon` / `branding.color` are required to publish; keep them set.
-- The publishing org must have 2FA enabled.
+- [Releasing](docs/releasing.md) — the `vX.Y.Z` (immutable) and `vX` (movable)
+  tag model and the steps to cut a release. Read before tagging or moving a tag.
+- [Marketplace constraints](docs/marketplace.md) — rules the published
+  `action.yml` must satisfy. Read before editing it.

docs/marketplace.md

@@ -0,0 +1,9 @@
+# Marketplace constraints
+
+Honor these when editing `action.yml`:
+
+- `name` must be globally unique across all Marketplace actions, users, and
+  orgs — hence the `OSSystems` prefix.
+- `description` must be under 125 characters.
+- `branding.icon` / `branding.color` are required to publish; keep them set.
+- The publishing org must have 2FA enabled.

docs/releasing.md

@@ -0,0 +1,31 @@
+# Releasing
+
+## Versioning
+
+Two kinds of tags, both on the same release commit:
+
+- `vX.Y.Z` (e.g. `v1.0.0`) — **immutable**. Matches a published Marketplace
+  release; never move it once published.
+- `vX` (e.g. `v1`) — **movable major tag**. Most callers pin `@v1`, so it must
+  be fast-forwarded to each new release on the same major line. `v1` is a *tag*,
+  not a branch.
+
+## Cutting a new release
+
+1. Land all changes on `main`.
+2. Tag the immutable version and push it:
+   ```
+   git tag -a vX.Y.Z -m "vX.Y.Z" && git push origin vX.Y.Z
+   ```
+3. Move the major tag to the same commit:
+   ```
+   git tag -f vX HEAD && git push -f origin vX
+   ```
+4. Create the GitHub release from the `vX.Y.Z` tag
+   (`gh release create vX.Y.Z --title vX.Y.Z --notes ...`). On the **first**
+   release of a major line, also check "Publish this Action to the GitHub
+   Marketplace" in the release UI (the Marketplace checkbox is UI-only) and
+   accept the Developer Agreement.
+
+For a docs/non-release change that should reach `@v1` callers without a new
+version, just move the major tag: `git tag -f v1 HEAD && git push -f origin v1`.