feat: Coverage-Drohne (sin-code cover) with scan, check, gaps, generate, hook

cmd/sin-code/cover_cmd.doc.md

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+# `sin-code cover`
+
+Coverage-Drohne — a state-of-the-art coverage automation tool for SIN-Code.
+
+## Subcommands
+
+- `scan` — print package coverage table (text or JSON).
+- `check` — fail CI if any package is below `--min` coverage.
+- `gaps` — list uncovered functions/blocks per package.
+- `generate` — write an AI test-generation request JSON.
+- `hook` — print or install a git pre-commit coverage gate.
+
+## SOTA design
+
+Coverage-Drohne combines the best practices from industrial LLM test-generation
+(Meta TestGen-LLM, Qodo Cover) with Go-native tooling:
+
+1. **Coverage-driven**: every run produces a machine-readable coverage profile.
+2. **Gap-aware**: `gaps` pinpoints the exact functions and blocks that are
+   not covered.
+3. **AI test-gen requests**: `generate` emits a JSON prompt that can be fed to
+   the agent loop or to an external LLM to produce the missing tests.
+4. **CI gate**: `check --min 100` is deterministic and can be used as a
+   merge-blocking gate.
+
+Future versions will add mutation-testing integration (`go-mutesting`),
+coverage-guided fuzzing (`go test -fuzz`), and a file-watcher that auto-triggers
+test generation after `sin-code` writes or edits a Go file.
+
+## Usage
+
+```bash
+sin-code cover scan
+sin-code cover scan --json
+sin-code cover check --min 100
+sin-code cover gaps --package coverdrohne
+sin-code cover generate --package coverdrohne --out req.json
+sin-code cover hook
+sin-code cover hook --install
+```
+
+## Exit codes
+
+- `0` — scan/check passed, no package below threshold.
+- `1` — check found a package below threshold (text mode) or a command error.
+
+## Machine-readable output
+
+`cover check --json` always exits `0` and prints a JSON envelope:
+
+```json
+{
+  "passed": false,
+  "min": 100,
+  "failed": [
+    {"import_path": "...", "coverage": 42.0, "statements": 100, "covered": 42}
+  ]
+}
+```

cmd/sin-code/cover_cmd.go

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+// SPDX-License-Identifier: MIT
+// Purpose: `sin-code cover` — Coverage-Drohne entry point.
+// Subcommands:
+//   cover scan       # package coverage table
+//   cover check      # CI gate with --min
+//   cover gaps       # uncovered functions/blocks
+//   cover generate   # AI test-generation request JSON
+//
+// Driver logic lives in cmd/sin-code/internal/coverdrohne.
+// Docs: cover_cmd.doc.md
+package main
+
+import (
+	"github.com/spf13/cobra"
+
+	"github.com/OpenSIN-Code/SIN-Code/cmd/sin-code/internal/coverdrohne"
+)
+
+// NewCoverCmd returns the `sin-code cover` subcommand.
+func NewCoverCmd() *cobra.Command {
+	return coverdrohne.NewCommand()
+}