feat: add --skip-var-renames quick check

[longvo92]

What

A new opt-in flag, --skip-var-renames, for sweeping a regenerate to find what is not a rename.

When a model update renames a wave of variables, the renames bury everything else. With this flag on, a C/C++ hunk whose every line is a binding differing only by variable names is folded as assumed-rename instead of real.

A binding is one statement that names an object and at most copies a single other object or literal into it. Either side may be a plain lvalue path, which is how Embedded Coder reaches its ports and state:

a = b;                     →  x = b;
acc_cmd = rtU.Pedal;       →  drv_cmd = rtU.Pedal;
rtY.Out = filt_in;         →  rtY.Out = filt_val;
buf[2] = rtDW->State;      →  buf[2] = rtDW->Level;
real_T filt_in;            →  real_T filt_val;
boolean_T flag = FALSE;    →  boolean_T other = FALSE;

Why this one is different

Every other rule in the engine proves the difference is noise before folding it. This one does not, and the repo rule says so: if a difference cannot be proven to be noise, it is a real change. A rewiring has exactly the same shape as a rename, so a run using this flag can be missing a real change.

That trade is the point of the flag, so it is contained rather than hidden:

• off by default, and it has to be asked for by name;
• what it folds keeps its own kind, assumed-rename — never spelled rename on any surface;
• the terminal summary prints a QUICK CHECK warning above the counts;
• the HTML report carries a one-line note between the folder tree and the diffs;
• the JSON output carries "quick_check": "skip-var-renames";
• the viewer title bar says QUICK CHECK: variable renames skipped.

What still counts as a real change, even with the flag on

• a changed literal — a = 0; → x = 1;
• a changed type — sint32 a = 0; → uint8 x = 0;
• an ALL_CAPS macro or enum constant on either side — flag = FALSE; → flag = TRUE;, mode = IDLE; → mode = DRIVE;
• a variable swap (a ↔ b), however consistent it looks
• any hunk holding one line that is not a binding — an expression, a call, a cast, an address-of, a prototype. One such line leaves the whole hunk real.

Verdicts, counts, exit codes and the ARXML/A2L path are untouched when the flag is absent.

Also in here

Report file headers now carry only the verdict badge. The Affected: <fn> hint and the noise-kind list are gone — a header answers "must I read this file", and the badge is that answer. The enclosing function is still captioned above each hunk (ƒ Calc_step), and a revealed noise group's placeholder row still names its kind.

Testing

tests/test_skip_var_renames.py (35 tests) covers the binding grammar, the map, the fold, every "still real" case above, and the four announcement surfaces.

python -m unittest discover -s tests    # 791 passed
python -m ruff check .                  # clean

🤖 Generated with Claude Code