chore: import upstream snapshot with attribution

.github/ISSUE_TEMPLATE/test_coverage_task.yml

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+name: Test Coverage Task
+description: Create a focused coverage-improvement issue tied to concrete files and targets
+title: "[Coverage] "
+labels: ["test", "coverage"]
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Use this template for scoped coverage work. Keep it tied to specific files, measurable targets, and the gate that must stay green.
+
+  - type: input
+    id: baseline
+    attributes:
+      label: Current Coverage Baseline
+      description: "Paste the current overall or file-level coverage number that justifies this task."
+      placeholder: "e.g. Lines 79.00%, Branches 72.85%, open-sse/handlers/chatCore.ts = 67.22%"
+    validations:
+      required: true
+
+  - type: textarea
+    id: scope
+    attributes:
+      label: Target Files Or Modules
+      description: "List the concrete source files or directories that this task will cover."
+      placeholder: |
+        Example:
+        - open-sse/handlers/chatCore.ts
+        - open-sse/services/combo.ts
+        - tests/integration/chat-pipeline.test.ts
+    validations:
+      required: true
+
+  - type: textarea
+    id: scenarios
+    attributes:
+      label: Missing Scenarios
+      description: "Describe the specific behaviors, branches, or failure paths that are currently uncovered."
+      placeholder: |
+        Example:
+        - Upstream timeout path
+        - Empty tool_calls normalization
+        - Fallback route after first provider failure
+    validations:
+      required: true
+
+  - type: input
+    id: target
+    attributes:
+      label: Coverage Target
+      description: "Set the expected target for this task."
+      placeholder: "e.g. Raise open-sse/handlers to 80%+ lines and keep global gate >= 60%"
+    validations:
+      required: true
+
+  - type: textarea
+    id: validation
+    attributes:
+      label: Validation Commands
+      description: "List the commands that must pass before this issue can be closed."
+      placeholder: |
+        Example:
+        - node --import tsx --test tests/unit/my-suite.test.ts
+        - npm run test:coverage
+    validations:
+      required: true
+
+  - type: textarea
+    id: notes
+    attributes:
+      label: Notes
+      description: "Optional context, blockers, or dependencies."
+    validations:
+      required: false