feat(#1877): restructure hive-forge into pr/issue sub-verbs

Group issue/PR operations under `pr` and `issue` parent commands
(`hive-forge pr close 42`, `issue create …`, `pr status --pr 42`) per the
operator decision — kind-namespaced verbs replace the flat surface.

- new `verbs::pr_cmd` / `verbs::issue_cmd` parent commands wrap the existing
  per-verb modules (reuse their Args + run fns) under `#[command(subcommand)]`.
- kind-validation (the win over the old generic verbs): the generics that work
  on both (view/comment/comments/close/labels/assign/timeline) call
  `assert_kind` first, so `pr close <issue>` / `issue close <pr>` are rejected
  with a 'use the other command' message. PR-only / issue-only verbs are
  kind-correct by construction. `number` exposed `pub(crate)` on the shared
  verbs so the wrappers can probe it.
- every flat kind verb (`close`, `pr-create`, `pr-status`, `issue-edit`, …)
  kept as a `#[command(hide = true)]` back-compat alias — still parses, dropped
  from --help; removed in a later sweep once usage migrates. (`pr`/`issue`
  bare-show become `pr show` / `issue show` — the names are now parents.)
- docs/tools/forge.md documents the new surface + the deprecated aliases.

cargo build/clippy/fmt clean, 54 tests pass; --help surface + alias parsing
smoke-tested.

docs/tools/forge.md

@@ -12,7 +12,25 @@ as a proper Rust binary). Use it instead of ad-hoc curl pipelines.
 
 ## Verbs
 
+**Kind-namespaced commands (preferred):** issue/PR operations are grouped
+under `issue` and `pr` parent commands — `hive-forge pr close 42`,
+`hive-forge issue create --title …`, `hive-forge pr status --pr 42`. The
+`pr <verb>` / `issue <verb>` forms validate the number's kind (e.g. `pr close`
+refuses an issue number, which the old generic `close` couldn't). Run
+`hive-forge pr --help` / `hive-forge issue --help` for the full subcommand
+list (show/create/edit/status/merge/reviews/commits/diff/view/comment/
+comments/close/labels/assign/timeline as applicable).
+
+The flat forms below (`close 42`, `pr-create …`, `pr-status …`, …) still work
+as **hidden back-compat aliases** during the transition and are dropped from
+`--help`; prefer the namespaced form. They'll be removed in a later sweep.
+
 ```bash
+hive-forge pr close 42                      # close a PR (kind-validated)
+hive-forge issue close 42                   # close an issue (kind-validated)
+hive-forge pr status --pr 42                # PR health (mergeable / CI / reviews)
+hive-forge issue create --title "..." --body "..."
+# --- flat aliases below remain valid (hidden) ---
 hive-forge view 42                          # title + body + comments
 hive-forge comments 42                      # list all comments (human-readable)
 hive-forge comments 42 --tail 10            # last 10 comments (count-then-page; efficient on long threads)