chore: scrub #NNN issue references from code comments and nix descriptions

Part of the docs-migration chore (issue #708). Remove GitHub issue
numbers from inline comments, option descriptions, and rustdoc —
these are contextless noise for anyone reading the code without
access to the original discussions. Replace with prose that captures
the same rationale directly.

No functional change. Build still clean (cargo check passes).

nix/packages/hive-forge-tools.nix

@@ -1,5 +1,5 @@
 { pkgs, lib }:
-# hive-forge — Forgejo CLI wrapper for hyperhive (closes #280).
+# hive-forge — Forgejo CLI wrapper for hyperhive.
 #
 # Previously a ~600-line bash script. Rewritten as a proper Rust
 # binary in `/hive-forge` so we get:
@@ -7,8 +7,7 @@
 #     reading the case statement),
 #   - one reqwest client with consistent error surfaces (no more
 #     `curl --fail-with-body` repeated per verb),
-#   - sane shell quoting (no more HEREDOC-eaten-by-positional traps
-#     like #379),
+#   - sane shell quoting (no more HEREDOC-eaten-by-positional traps),
 #   - and a single test surface.
 #
 # This Nix file is now a thin extractor: it pulls just the