🗑️ remove(skills): drop unused skills and update references

codex/skills/systematic-debugging/SKILL.md

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----
-name: systematic-debugging
-description:
-  "Systematic debugging for bugs, failing tests, regressions (TSL/C++/Python).
-  Triggers: debug, failing test, regression, crash, 复现, 定位, 排查, 调试."
----
-
-# Systematic Debugging（系统化调试）
-
-## When to Use
-
-- Bugs, crashes, failing/flaky tests, regressions
-- “It doesn’t work” reports with unclear reproduction
-
-## Inputs（required）
-
-- Expected vs actual behavior
-- Repro command/steps (or best-known approximation)
-- Logs/traces/screenshots/error output
-- Environment details (OS, versions, configs)
-
-## Procedure（default）
-
-1. **Reproduce**
-   - Make the failure deterministic if possible
-   - Minimize repro steps (smallest input/command)
-
-2. **Localize**
-   - Identify failing component and boundary conditions
-   - Add temporary logging/assertions if needed (then remove)
-
-3. **Hypothesize & Test**
-   - Form a small number of hypotheses
-   - Design quick experiments to falsify each hypothesis
-
-4. **Fix & Verify**
-   - Fix the root cause (not just symptoms)
-   - Add/update tests; rerun the minimal relevant suite
-
-## Output Contract（stable）
-
-- Repro: exact steps/command
-- Diagnosis: root cause + evidence
-- Fix: what changed + why it works
-- Verification: commands + outputs/exit codes
-- Follow-ups: hardening or cleanup tasks
-
-## Guardrails
-
-- Avoid changing multiple variables at once
-- Prefer instrumentation and evidence over guessing
-- Keep fixes minimal and scoped