Add Copilot skill architecture with 10 skills, 2 agents, and shared infra

Introduce .github/skills/ with solve, prove, optimize, simplify,
encode, explain, benchmark, memory-safety, static-analysis, and
deeptest skills. Each skill follows a SKILL.md + scripts/ pattern
with Python scripts backed by a shared SQLite logging library
(z3db.py). Two orchestrator agents (z3-solver, z3-verifier) route
requests to the appropriate skills.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.github/skills/solve/scripts/solve.py

@@ -0,0 +1,66 @@
+#!/usr/bin/env python3
+"""
+solve.py: check satisfiability of an SMT-LIB2 formula via Z3.
+
+Usage:
+    python solve.py --formula "(declare-const x Int)(assert (> x 0))(check-sat)(get-model)"
+    python solve.py --file problem.smt2
+    python solve.py --file problem.smt2 --debug --timeout 60
+"""
+
+import argparse
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent.parent / "shared"))
+from z3db import Z3DB, run_z3, parse_model, parse_unsat_core, setup_logging
+
+
+def main():
+    parser = argparse.ArgumentParser(prog="solve")
+    parser.add_argument("--formula", help="SMT-LIB2 formula string")
+    parser.add_argument("--file", help="path to .smt2 file")
+    parser.add_argument("--timeout", type=int, default=30)
+    parser.add_argument("--z3", default=None, help="path to z3 binary")
+    parser.add_argument("--db", default=None)
+    parser.add_argument("--debug", action="store_true")
+    args = parser.parse_args()
+
+    setup_logging(args.debug)
+
+    if args.file:
+        formula = Path(args.file).read_text()
+    elif args.formula:
+        formula = args.formula
+    else:
+        parser.error("provide --formula or --file")
+        return
+
+    db = Z3DB(args.db)
+    run_id = db.start_run("solve", formula)
+
+    result = run_z3(formula, z3_bin=args.z3, timeout=args.timeout, debug=args.debug)
+
+    model = parse_model(result["stdout"]) if result["result"] == "sat" else None
+    core = parse_unsat_core(result["stdout"]) if result["result"] == "unsat" else None
+
+    db.log_formula(run_id, formula, result["result"],
+                   str(model) if model else None)
+    db.finish_run(run_id, result["result"], result["duration_ms"],
+                  result["exit_code"])
+
+    print(result["result"])
+    if model:
+        for name, val in model.items():
+            print(f"  {name} = {val}")
+    if core:
+        print("unsat core:", " ".join(core))
+    if result["stderr"] and result["result"] == "error":
+        print(result["stderr"], file=sys.stderr)
+
+    db.close()
+    sys.exit(0 if result["exit_code"] == 0 else 1)
+
+
+if __name__ == "__main__":
+    main()