Add /techdebt claude skill (#10515)

* feat(ai): Add techdebt claude skill
* feat(ai): Remove unnecessary examples
* feat(ai): Simplify the skill to be more focused
* feat(ai): Add skill metadata
* fix(ai): Fix diff to compute merge base first

Author: PerfectSlayer

.claude/skills/techdebt/SKILL.md

@@ -0,0 +1,67 @@
+---
+name: techdebt
+description: Analyze branch changes for technical debt, code duplication, and unnecessary complexity
+user-invocable: true
+context: fork
+allowed-tools:
+  - Bash
+  - Read
+  - Grep
+  - Glob
+---
+
+# Techdebt Cleanup Skill
+
+Analyze changes on the current branch to identify and fix technical debt, code duplication, and unnecessary complexity.
+
+## Instructions
+
+### Step 1: Get Branch Changes
+
+Find the merge-base (where this branch diverged from master) and compare against it:
+
+```bash
+# Find upstream (DataDog org repo)
+UPSTREAM=$(git remote -v | grep -E 'DataDog/[^/]+(.git)?\s' | head -1 | awk '{print $1}')
+if [ -z "$UPSTREAM" ]; then
+  echo "No DataDog upstream found, using origin"
+  UPSTREAM="origin"
+fi
+
+# Find the merge-base (commit where this branch diverged from master)
+MERGE_BASE=$(git merge-base HEAD ${UPSTREAM}/master)
+echo "Comparing changes introduced on this branch since diverging from master using base commit: $MERGE_BASE"
+
+git diff $MERGE_BASE --stat
+git diff $MERGE_BASE --name-status
+```
+
+If no changes exist, inform the user and stop.
+
+If changes exist, read the diff and the full content of modified source files (not test files) to understand context.
+
+### Step 2: Analyze for Issues
+
+Look for:
+
+**Code Duplication**
+- Similar code blocks that should be extracted into shared functions
+- Copy-pasted logic with minor variations
+
+**Unnecessary Complexity**
+- Over-engineered solutions (abstractions used only once)
+- Excessive indirection or layers
+- Backward compatibility shims that aren't needed
+
+**Redundant Code**
+- Dead code paths
+- Overly defensive checks for impossible scenarios
+
+### Step 3: Report and Fix
+
+Present a concise summary of issues found with file:line references.
+
+Then ask the user if they want you to fix the issues. When fixing:
+- Make one logical change at a time
+- Do NOT change behavior, only refactor
+- Skip trivial or stylistic issues