Add CCZ and CCX gate support

[glasses666]

Closes #113.

Summary

• Add CCZ and CCX/Toffoli support by expanding both program-text shorthand and Circuit.append() calls into the existing Clifford+T instruction set.
• Use the 7-T CCZ decomposition discussed in the issue, with CCX derived by H-conjugating the target.
• Add matrix truth-table coverage for CCZ and CCX, plus shorthand-vs-append coverage.
• Update the README and docs quick-start supported-instruction lists.

Scope note

Visualization support is left out intentionally, matching the issue discussion that SVG visualization can be deferred.

Validation

• PYTHONPATH=src uv run pytest -q -> 1087 passed in 46.24s
• PYTHONPATH=src uv run pytest test/unit/test_circuit.py -q -> 192 passed in 1.22s
• PYTHONPATH=src uv run pytest test/integration/test_gate_unitaries.py -q -> 117 passed in 2.27s
• PYTHONPATH=src uv run ruff check src/tsim/utils/program_text.py src/tsim/circuit.py test/unit/test_circuit.py -> All checks passed!
• PYTHONPATH=src uv run black --check src/tsim/utils/program_text.py src/tsim/circuit.py test/unit/test_circuit.py -> 3 files would be left unchanged
• PYTHONPATH=src uv run pyright src/tsim/circuit.py src/tsim/utils/program_text.py test/unit/test_circuit.py -> 0 errors, 0 warnings, 0 informations

Note: in my local checkout, bare uv run pytest did not put src/ on sys.path, so I used PYTHONPATH=src for the validation commands above.

AI disclosure

AI-assisted with OpenAI Codex; the diff was reviewed and locally verified before submission.

[rafaelha]

Thanks for the contribution, this looks great! Could you also add support for tags?

Currently,

c = tsim.Circuit("""
X 0
CCX[tag] 0 1 2
M 2
""")

fails with

ValueError: Could not parse 'CCX' in program text.

The expected behavior is to expand the CCX with tags, i.e.

X 0
H[tag] 2
CX[tag] 1 2
T_DAG[tag] 2
CX[tag] 0 2
T[tag] 2
CX[tag] 1 2
T_DAG[tag] 2
CX[tag] 0 2
T[tag] 1 2
CX[tag] 0 1
T[tag] 0
T_DAG[tag] 1
CX[tag] 0 1
H[tag] 2
M 2

I think after that, this is good to be merged!

[glasses666]

Fixed in the latest push. CCX[tag] and CCZ[tag] now preserve the tag across the expanded gates, and the exact CCX[tag] example is covered by a unit test.

Local checks passed: pytest -q (1093 passed), ruff check src test, black --check, and targeted pyright.