feat(#1399): hive-forge clone verb + pr-create --agit for no-fork PRs

docs/tools/forge.md

@@ -53,8 +53,38 @@ hive-forge attach-comment 18042 /path/to/file  # upload a file attachment to a c
 hive-forge attachment-get <uuid>            # download an attachment; prints resolved path to stdout
 hive-forge subscription --watch             # subscribe to repo notifications
 hive-forge subscription --unwatch           # unsubscribe
+hive-forge -r internal/knowledge clone      # clone with creds auto-injected
+hive-forge -r internal/knowledge pr-create --agit --topic foo --title "..."  # open PR via AGit (no fork)
 ```
 
+### Contributing to a read-only repo (`clone` + `pr-create --agit`)
+
+Agents are read-only collaborators on some repos (e.g.
+`internal/knowledge`) and so can't push branches. Forgejo's AGit flow
+lets a read-only user open a PR by pushing the current `HEAD` to the
+magic ref `refs/for/<base>/<topic>`. Two verbs cover the workflow:
+
+```
+hive-forge -r internal/knowledge clone          # clone with token auto-injected
+cd knowledge
+# add / edit / delete any files, then commit normally
+git add -A && git commit -m "add foo runbook"
+hive-forge -r internal/knowledge pr-create --agit \
+  --topic foo-runbook \    # groups pushes into ONE PR; reuse to update it
+  --title "add foo runbook" \
+  [--body "details"]       # PR description (also accepts --body-file)
+```
+
+`clone` derives the dest dir from the repo basename (override with a
+positional arg); `--branch` / `--depth` are passed through. The token
+is injected into the clone's `origin` remote so `pr-create --agit`
+(default remote `origin`) can push without re-auth.
+
+`pr-create --agit` prints the PR URL. Re-running with the same
+`--topic` force-updates the existing open PR (the AGit ref is
+agent-owned scratch). Opens a reviewable PR the operator merges — never
+commits straight to `main`.
+
 `hive-forge <verb> --help` prints the full signature for any verb.
 
 ### `pr-status`