chore: update coverage requirements and testing protocols across agent instructions and guidelines

.github/instructions/copilot-instructions.md

@@ -108,7 +108,7 @@ Before marking an implementation task as complete, perform the following in orde
     - Do not output code that violates pre-commit standards.
 
 3. **Coverage Testing** (MANDATORY - Non-negotiable):
-    - **MANDATORY**: Patch coverage must cover 100% of new/modified code. This prevents CodeCov Report failing CI.
+    - **MANDATORY**: Patch coverage must cover 100% of modified lines (Codecov Patch view must be green). If patch coverage fails, add targeted tests for the missing patch line ranges.
     - **Backend Changes**: Run the VS Code task "Test: Backend with Coverage" or execute `scripts/go-test-coverage.sh`.
         - Minimum coverage: 85% (set via `CHARON_MIN_COVERAGE` or `CPM_MIN_COVERAGE`).
         - If coverage drops below threshold, write additional tests to restore coverage.

.github/instructions/taming-copilot.instructions.md

@@ -24,6 +24,7 @@ This section outlines the absolute order of operations. These rules have the hig
 -   **Standard First**: Heavily favor standard library functions and widely accepted, common programming patterns. Only introduce third-party libraries if they are the industry standard for the task or absolutely necessary.
 -   **Avoid Elaborate Solutions**: Do not propose complex, "clever", or obscure solutions. Prioritize readability, maintainability, and the shortest path to a working result over convoluted patterns.
 -   **Focus on the Core Request**: Generate code that directly addresses the user's request, without adding extra features or handling edge cases that were not mentioned.
+-   **Spec Hygiene**: When asked to update a plan/spec file, do not append unrelated/archived plans; keep it strictly scoped to the current task.
 
 ## Surgical Code Modification
 

.github/instructions/testing.instructions.md

@@ -16,3 +16,5 @@ description: 'Strict protocols for test execution, debugging, and coverage valid
 ## 3. Coverage & Completion
 * **Coverage Gate:** A task is not "Complete" until a coverage report is generated.
 * **Threshold Compliance:** You must compare the final coverage percentage against the project's threshold (Default: 85% unless specified otherwise). If coverage drops, you must identify the "uncovered lines" and add targeted tests.
+* **Patch Coverage Gate (Codecov):** If production code is modified, Codecov **patch coverage must be 100%** for the modified lines. Do not relax thresholds; add targeted tests.
+* **Patch Triage Requirement:** Plans must include the exact missing/partial patch line ranges copied from Codecov’s **Patch** view.