fix: align math/tonumber/format/table.insert-remove with Lua 5.4 semantics

[esrrhs]

fix: align math/tonumber/format/table.insert-remove with Lua 5.4 semantics

Found by a third differential-testing pass against Lua 5.4.9 (semantics
verified against the 5.4.6 sources: lmathlib.c, lobject.c l_str2d,
lstrlib.c str_format, ltablib.c).

math library:

• math.floor/ceil now follow Lua's pushnumint: results that fit in
  int64 are returned as integer; inf/-inf/nan/values >= 2^63 stay
  float instead of always returning float.
• math.fmod distinguishes integer pairs (integer result, C truncation
  semantics; divisor zero raises, mininteger % -1 is 0) from mixed/
  float pairs (always float, divide-by-zero is NaN, no error).
• math.modf integer part truncates toward zero and returns integer when
  integral; fractional part is +0.0 when there is no fraction (integer
  values and inf), matching lua 5.4 including modf(inf)=(inf, 0.0).

tonumber:

• reject 'inf'/'nan' spellings in any case (Lua only accepts constructed
  math.huge/0/0, never literals), while accepting exponent overflow:
  tonumber('1e999') -> inf, '1e-999' -> 0.0, hex floats likewise.
  Unify the three parser paths (boost charconv decimal, strtod fallback,
  JIT inline FlTonumber) on l_str2d rules; ERANGE saturates via strtod.

string.format:

• %d %i %u %x %X %o %c now require an exact integer via the
  checkinteger rule (3.9, 1e20, inf raise 'number has no integer
  representation') instead of silently truncating; exact-value floats
  like 2.0 still work.
• unknown conversion specifiers and dangling '%' raise 'invalid
  conversion' instead of being copied through verbatim (covers %z,
  '%1', '%.f'; Lua does not support '' either).

table.insert / table.remove:

• insert raises 'position out of bounds' when pos is outside
  [1, #t+1] (incl. negatives and non-integer floats) instead of
  silently doing nothing / creating holes.
• remove validates only an explicitly given position against
  [1, #t+1]; the default/nil position (= #t, including empty tables)
  stays unchecked; pos == #t+1 is valid and returns nil, and no longer
  wipes t[#t].

JIT parity: floor/ceil/fmod/modf/insert/remove had inline code
generation in c_gen that bypassed the natives, so the native fixes
alone left TCC/GCC on the old behavior. Add FlPushNumInt/FlMathFloor/
FlMathCeil/FlMathFmod/FlMathModf to c_runtime_header.h and route both
the JIT inline paths and the natives through the shared implementation.

Note: the runtime header is embedded in c_gen as an R"( raw string, so
the fmod error message cannot end right before a quote (')' + quote
would terminate the raw literal).

Tests: add test_math_lua54_types, test_basic_tonumber_lua54,
test_format_lua54_strict (all run on TCC/GCC/interp); rewrite
test_math_fmod_zero and the table boundary tests that encoded the old
silent/out-of-range behavior. Differential suite: 0 divergence on the
math/table/number cases; full 1515-test suite passes.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 94.02985% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.20%. Comparing base (6081541) to head (30a9c0d).

Files with missing lines	Patch %	Lines
src/compile/c_gen.cpp	76.92%	3 Missing ⚠️
src/native/basic/native_basic.cpp	95.23%	1 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master      #27      +/-   ##
==========================================
+ Coverage   88.07%   88.20%   +0.12%     
==========================================
  Files         124      124              
  Lines       25234    25248      +14     
==========================================
+ Hits        22225    22269      +44     
+ Misses       3009     2979      -30     

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