Judge a block parameter by which parameter it is, not only by its value

[ww-mw]

A user clicked three links the Usage column had drawn and nothing happened. Two of the
three rows should never have existed: a Bus Selector's OutputSignals=a,b and a Math
Function's Operator=square are not references to data at all. (The dead link is a
renderer defect and is fixed in the VS Code repo; the rows are this package's.)

What was wrong

The <P> gate was a property blocklist plus a value test, and neither can see the
difference between Gain=square and Operator=square — square is a legal variable
name, so the value test has to say yes. What rules it out is which parameter holds
it: Operator is an option list of fifteen choices Simulink itself enforces. That is
a fact about the block type, which the gate never had.

The cost was not a spare row. On a MATLAB-written model whose bus carries a signal a
while the model workspace also holds a variable a, Simulink.findVars gives a no
users at all — and this package put the Bus Selector on it. A false reverse edge,
and one a reader cannot tell from a true one.

The fix

isParamReference now takes the block type and consults two measured tables:

• ENUM_BLOCK_PARAMS — 343 (BlockType, parameter) pairs generated by the new
  gen_block_params.m from DialogParameters over every block in simulink and
  simulink_extras. A pair is emitted only when it is an option list on every
  instance: SubSystem|OutDataTypeStr is free text on a plain subsystem and a menu on a
  masked one, and suppressing the free-text case would hide a real
  Simulink.NumericType reference.
• a three-entry hand list of free-text parameters findVars measurably never
  credits — a Bus Selector's OutputSignals, a Bus Assignment's AssignedSignals, and
  a Model block's file name under all three spellings. Not derivable from any dialog
  property, so probe_non_data_params.m asks MATLAB directly, on models built so the
  answer is sharp.

Keying on the pair is what makes suppression safe: Operator is a menu on a Math
block and an expression on a Gain. A block type in neither table — every toolbox block,
every masked library link — is judged exactly as before, which is the direction #9
argues for: a spare row is a row a reader ignores, a suppressed reference is a Usage
cell that lies by omission.

Two other rules were measured first and both are wrong, both by hiding real
references — the dont-eval attribute, and "set_param refuses an identifier". Both
are written out in the generator's header so they are not re-derived.

enumBlockParams.ts is generated into src/ rather than into a fixture directory,
because the parser imports it at parse time; drift.mjs now regenerates and diffs it
per block type, since a release that turned a menu into free text would leave the suite
green and a reference hidden.

Tests

blockParamUsages.test.ts — 7 of its cases fail with the fix reverted — covering the
pair-keying itself, the mask parameters the gate must not reach, the parameters that
must stay admitted (ParameterArgumentValues), and the .slx and .mdl of the same
three blocks held against each other rather than against a literal. Full suite:
4328 pass, npm run verify green.