refactor(circuit): Only flatten circuit when a ZX graph is constructed

[rafaelha]

This gives better visualization for circuits with repeat blocks and now also correctly applies SHIFT_COORD instructions.

[github-actions]

☂️ Python Coverage

current status: ✅

Overall Coverage

Lines	Covered	Coverage	Threshold	Status
1965	1910	97%	0%	🟢

New Files

No new covered files...

Modified Files

File	Coverage	Status
src/tsim/circuit.py	100%	🟢
src/tsim/utils/diagram.py	94%	🟢
TOTAL	97%	🟢

updated for commit: 42a58fd by action🐍

[github-actions]

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[Copilot]

Pull request overview

Refactors Circuit to preserve REPEAT blocks by default (improving visualization and keeping loop structure intact), while still flattening at ZX-graph construction time where needed.

Changes:

• Stop auto-flattening circuits on construction/append/multiply; add an explicit Circuit.flattened() helper.
• Update diagram placeholder replacement to work with circuits containing REPEAT blocks.
• Add/adjust unit tests to validate repeat-block behavior across diagrams, parsing, and circuit operations.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/tsim/circuit.py	Preserves repeat blocks in core circuit wrapper; introduces flattened() and adjusts methods affected by non-flattened circuits.
src/tsim/utils/diagram.py	Refactors tagged-gate replacement to recurse into repeat blocks instead of asserting none exist.
src/tsim/utils/encoder.py	Ensures encoder logic flattens its input circuit explicitly (since it assumes no repeat blocks).
test/unit/test_circuit.py	Updates expectations and adds coverage for preserving repeat blocks across operations/indexing/copying.
test/unit/core/test_parse.py	Adds parsing tests ensuring repeat blocks are flattened during ZX parse.
test/unit/utils/test_diagram.py	Adds diagram test ensuring repeat blocks are visualized (not flattened away).

Comments suppressed due to low confidence (1)

src/tsim/circuit.py:405

• without_annotations now iterates over self._stim_circ.flattened(), which expands all REPEAT blocks. That means calling without_annotations() will unexpectedly destroy loop structure (and can blow up circuit size) even though the method name suggests only removing annotations. Consider filtering annotations while preserving repeat blocks (e.g., recursively process stim.CircuitRepeatBlock bodies and re-wrap them).

        circ = stim.Circuit()
        for instr in self._stim_circ.flattened():
            assert not isinstance(instr, stim.CircuitRepeatBlock)
            if instr.name in ["OBSERVABLE_INCLUDE", "DETECTOR"]:
                continue
            circ.append(instr)
        return Circuit.from_stim_program(circ)

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