fix: gate PVT satellites on decoding completeness

[giove-a]

Summary

calc_pvt now admits a satellite into the solve only once its decoder has
fully decoded the navigation data a fix needs — not just that the satellite
reports healthy.

This pairs GNSSDecoder's newly exported is_decoding_completed_for_positioning
with the existing is_sat_healthy check:

healthy_indices = findall(
    x -> is_decoding_completed_for_positioning(x.decoder) && is_sat_healthy(x.decoder),
    states,
)

Completeness is checked first: once it holds, the broadcast health bit
is_sat_healthy inspects is guaranteed to have been decoded, so the two
predicates compose without a separate nothing guard.

Why

Previously a satellite could pass the health check while its decoder had not
yet recovered the full data set required to position from it (time of week,
ephemeris, SV clock polynomial, and — where carried in the required set — the
week number and single-band group delay). Using such a satellite risks a bad
or failed fix. The new gate ensures every satellite entering the least-squares
solve carries a complete, self-consistent data set.

Changes

• src/PositionVelocityTime.jl — add the is_decoding_completed_for_positioning
  gate alongside is_sat_healthy in calc_pvt.
• Project.toml — bump GNSSDecoder compat "3.6" → "3.7" (the release that
  exports the new function).

Testing

Verified against GNSSDecoder 3.7.0 that both the GPS L1 C/A and Galileo E1B
test fixtures' data blocks pass the new gate (and correctly fail when a
required field such as TOW/WN is dropped), so the existing test suite's
healthy-satellite counts are preserved.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.30%. Comparing base (e1976ef) to head (c91b115).

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #51   +/-   ##
=======================================
  Coverage   98.30%   98.30%           
=======================================
  Files           7        7           
  Lines         472      473    +1     
=======================================
+ Hits          464      465    +1     
  Misses          8        8           

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[github-actions]

Benchmark Results (Julia v1)

Time benchmarks

	master	c91b115...	master / c91b115...
calc_pvt/GPSL1/4sats/cold	0.0441 ± 0.0036 ms	0.044 ± 0.0063 ms	1 ± 0.17
calc_pvt/GPSL1/4sats/warm	0.0393 ± 0.0067 ms	0.0393 ± 0.0072 ms	1 ± 0.25
calc_pvt/GPSL1/9sats/cold	0.0639 ± 0.0022 ms	0.064 ± 0.0019 ms	0.999 ± 0.045
calc_pvt/GPSL1/9sats/warm	0.0399 ± 0.0011 ms	0.0398 ± 0.00098 ms	1 ± 0.036
calc_pvt/GalileoE1B/4sats/cold	0.0393 ± 0.007 ms	0.0394 ± 0.0079 ms	0.998 ± 0.27
calc_pvt/GalileoE1B/4sats/warm	19.1 ± 3.4 μs	18.9 ± 3 μs	1.01 ± 0.24
calc_pvt/GalileoE1B/5sats/cold	0.0421 ± 0.0071 ms	0.0423 ± 0.0072 ms	0.996 ± 0.24
calc_pvt/GalileoE1B/5sats/warm	22 ± 4.5 μs	22 ± 4.2 μs	1 ± 0.28
time_to_load	2.51 ± 0.03 s	2.51 ± 0.063 s	0.997 ± 0.028

Memory benchmarks

	master	c91b115...	master / c91b115...
calc_pvt/GPSL1/4sats/cold	0.552 k allocs: 25.2 kB	0.552 k allocs: 25.2 kB	1
calc_pvt/GPSL1/4sats/warm	0.493 k allocs: 21.5 kB	0.493 k allocs: 21.5 kB	1
calc_pvt/GPSL1/9sats/cold	0.78 k allocs: 31.5 kB	0.78 k allocs: 31.5 kB	1
calc_pvt/GPSL1/9sats/warm	0.622 k allocs: 21.7 kB	0.622 k allocs: 21.7 kB	1
calc_pvt/GalileoE1B/4sats/cold	0.541 k allocs: 24.5 kB	0.541 k allocs: 24.5 kB	1
calc_pvt/GalileoE1B/4sats/warm	0.372 k allocs: 14.7 kB	0.372 k allocs: 14.7 kB	1
calc_pvt/GalileoE1B/5sats/cold	0.58 k allocs: 25.2 kB	0.58 k allocs: 25.2 kB	1
calc_pvt/GalileoE1B/5sats/warm	0.422 k allocs: 15.9 kB	0.422 k allocs: 15.9 kB	1
time_to_load	0.149 k allocs: 11.2 kB	0.149 k allocs: 11.2 kB	1