Fix variable manipulation and serialization

[ClementPasteau]

Before:

Enregistrement.de.l.ecran.2026-04-28.a.10.17.09.mov

After:

Enregistrement.de.l.ecran.2026-04-28.a.10.27.23.mov

Multiple fixes:

• boolean variable conditions initial value was "true" instead of "True"

  • it is now fixed so that when a new condition is added the default value
    is "True"
  • previous "true" were being read as "False" in the editor and the
    runtime, because != "True". This is kept as-is so no breaking change.
  • opening an instruction with "true" will now automatically convert it to
    "False" in the editor (normalize-on-load, not at serialization time).

• When adding a condition "Boolean variable is true/false" after having
  manipulated a "Number variable = x" the instruction was being serialized as
  "variable/=" ("=" was being pre-populated from the previous instruction
  because of the relational operator instead of being reset). It means the
  JSON contained "=" on a boolean condition.

  • We now reset those parameters when changing the type, and pick the first
    valid operator for the new instruction type (e.g. "True" for boolean, "="
    for number/string)
  • previous "=" were being read as "False" in the editor and the runtime,
    because != "True". This is kept as-is so no breaking change.
  • opening an instruction with "=" where it's not a valid value will now
    automatically convert it to "False" in the editor

• When editing a variable name inline (e.g. changing from var1 (number) to
  var2 (boolean)), the operator parameter was being corrected using the
  metadata of the old instruction type (captured when the inline editor
  opened), not the new one. This meant the reset picked operators from the
  wrong list — for example switching to a boolean variable could still end up
  with "=" in the JSON.

  • We now re-fetch the instruction metadata from the current instruction
    type at apply time, so the operator is always validated against the right
    list

• handle changing a variable type either in the variable declaration (ex:
  switch number->boolean) or in the instruction itself (changing from
  var1(number) to var2(boolean))

  • This used to keep wrong parameters in the JSON (ex: "=", "True" where
    they don't belong)
  • It now automatically converts the parameters to what they're most likely
    to be with the new type

• setupInstructionParameters now validates and corrects existing operator
  values, not just empty ones. Previously it only filled in a value when the
  parameter was empty, so a stale "startsWith" left on a NumberVariable
  condition (for example) would be silently kept. Now any value not in the
  valid set for that operator type is replaced with the first valid one.