refactor(forge): split forge-interaction into specialized GitHub and Gitea skills

Break the monolithic forge-interaction skill into focused, single-responsibility
skills for better predictability and maintainability:

- Add forge-github skill for GitHub-specific interactions using `gh` CLI
- Add forge-gitea skill for Gitea-specific interactions using `tea` CLI
- Convert forge-interaction into a router that delegates to specialized skills
- Add forge-router skill with model invocation disabled for guidance only
- Move all forge-related skills to common/deprecated directory

Each specialized skill now contains its own complete decision tree, CLI usage
patterns, and authentication checks for its respective forge platform.

common/deprecated/forge-preferences/triage-labels.md

@@ -0,0 +1,15 @@
+# Triage Labels
+
+The skills speak in terms of five canonical triage roles. This file maps those roles to the actual label strings used in this repo's issue tracker.
+
+| Label in mattpocock/skills | Label in our tracker | Meaning                                  |
+| -------------------------- | -------------------- | ---------------------------------------- |
+| `needs-triage`             | `needs-triage`       | Maintainer needs to evaluate this issue  |
+| `needs-info`               | `needs-info`         | Waiting on reporter for more information |
+| `ready-for-agent`          | `ready-for-agent`    | Fully specified, ready for an AFK agent  |
+| `ready-for-human`          | `ready-for-human`    | Requires human implementation            |
+| `wontfix`                  | `wontfix`            | Will not be actioned                     |
+
+When a skill mentions a role (e.g. "apply the AFK-ready triage label"), use the corresponding label string from this table.
+
+Edit the right-hand column to match whatever vocabulary you actually use.