[DSP-3] Issues tools: create/update/close/get + batch + link_issues from devswarm

[justrach]

Child of #53. Source: justrach/devswarm.

Tools to port (7)

DevSwarm tool	Purpose	Forge landing zone (proposed)
create_issue / update_issue / close_issue / get_issue	Individual issue ops on the active repo	forge_app + SDK issues.*, wrapping gh
create_issues_batch / close_issues_batch	Bulk ops	same
link_issues	Establish explicit dependency links	uses GitHub sub-issues API or task-list syntax

Acceptance criteria

• All ops respect the existing codegraff label taxonomy (priority:p0–p2, type:, work:, severity:, status:).
• create_issue enforces the issue template gate from DSP-2 — refuse to file an issue missing acceptance criteria for type: feature or repro steps for type: bug (devswarm #394).
• link_issues actually creates a parent/child relationship that GitHub renders, not just an appended body line (devswarm #393).
• Batch ops are idempotent — re-running with the same dedup key is a no-op.

Notes

This is the boring-but-load-bearing layer. The planner (DSP-2) and the orchestrator (DSP-1) both call into these.