fix: guard missing/unresolvable taxonomy in annotate/train + deterministic species selection

[vinvomero]

Ports the merged predict() taxonomy fix (#94) to the two entry points that never
adopted it, and makes species/lineage selection deterministic.

Problem

predict() was hardened in #94, but annotate() and train() still pass taxonomy
straight into choose_best_busco_species / choose_best_augustus_species. So:

• a False taxonomy (JGI lookup AND training-data taxonomy both unavailable)
  crashes with argument of type 'bool' is not iterable; and
• a non-matching taxonomy falls through best_taxonomy's random.choice() tie-break
  -- the "randomly picks a wrong Augustus species" path behind Problem on finding best augustus species #60, whose log
  shows a valid taxonomy resolving to augustus --species=elephant_shark, which
  then exits 1 inside the augustus binary.

Fix

• New augustus_species_from_taxonomy() -- the Augustus analog of the existing
  busco_lineage_from_taxonomy(). It delegates the FULL taxonomy to
  choose_best_augustus_species (Augustus scores all levels, exact=False), so
  resolvable inputs are byte-identical; guards falsy/non-overlapping taxonomy with
  a deterministic default + loud warning; always returns a valid augustus_species key.
• Route the busco sites in annotate()/train() through
  busco_lineage_from_taxonomy(..., default=None) with the same warn+default pattern
  predict() already uses.
• Make best_taxonomy's tie-break deterministic -- sorted(best_matches, key=str.lower)[0]
  instead of random.choice -- so selection is reproducible run-to-run. This is shared
  with the busco path; it only changes previously-random tie outcomes, and key=str.lower
  avoids a lexical bias toward the capitalized reference keys.

On #60

This makes the Augustus pick deterministic (no more random elephant_shark) and guards
the crash class. Whether a deterministic default species actually RUNS to completion for
an exotic non-fungal genome depends on the augustus binary -- hence "addresses" rather
than "fixes". For off-label genomes, --augustus_species remains the escape hatch (unchanged).

Tests

Extends tests/unit/test_utilities_taxonomy.py: falsy/empty -> default, byte-identical
delegation on working inputs (verified across all 100 augustus reference taxa),
deterministic + case-insensitive tie-break, overlap-gate default on malformed partial
taxonomy, default=None sentinel.

Addresses #60 (refs #32).