test(engine): pin the mana-spend commander resolution and Gilanra's spend-filter article (CR 903.3 + CR 106.6)

[matthewevans]

Ports the three regression pins from the parallel #77 checkpoint work
(commit 3126701d4a) onto the shipped implementation:

• path_of_ancestry_fires_for_a_deck_pool_registered_commander: the filter
  authority must see a commander known ONLY as a deck-pool registration
  (no command-zone object materialized). CR 106.6 + CR 903.3.
• path_of_ancestry_fires_for_a_commander_an_opponent_controls: CR 903.3
  makes the commander designation an attribute of the card retained across
  zones — owner/registration-scoped, so a STOLEN commander still fires its
  owner's Path of Ancestry. A controller-keyed scan silently breaks this.
• gilanra_mana_value_spend_trigger_survives_the_retype: the spend filter's
  leading article ('a spell with mana value 6 or greater') must parse; the
  shared grammar is written for the article-less next-spell phrasing and a
  bare 'a' would reject the clause, silently gapping a supported card.
  CR 106.6 + CR 202.3.

Both commander witnesses were watched RED under a controller-keyed naive
port during the checkpoint work; they pin the deck-pool-first resolution
the shipped FilterProp::SharesCreatureTypeWithCommander arm uses. The
spend filter is derived from the PARSER inside the test, so the witnesses
cannot drift from what the card actually lowers to.

[gemini-code-assist]

Code Review

This pull request adds a regression test to ensure that Gilanra's mana-value spend filter is correctly parsed and does not regress. The feedback recommends strengthening the test assertion by replacing a weak string-based check on the debug representation with a robust structural match on the parsed filter properties to verify the comparator and value.

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[gemini-code-assist]

This assertion is a bit weak for a regression pin. It only checks that the debug representation of the filter contains "Cmc", but doesn't validate the comparator (>=) or the value (6).

To make this test more robust and align with L3. Test adequacy from the style guide, it would be better to use a structural match on the FilterProp::Cmc to ensure the correct values are parsed.

    let TargetFilter::Typed(typed_filter) = filter else {
        panic!("expected a Typed filter for the mana-spend trigger, got {filter:?}");
    };
    assert!(
        typed_filter.properties.iter().any(|p| matches!(p, FilterProp::Cmc { comparator: Comparator::GE, value: QuantityExpr::Fixed { value: 6 } })),
        "the mana-value threshold must survive as a Cmc(GE, 6) predicate: {filter:?}"
    );

[github-actions]

Parse changes introduced by this PR

✓ No card-parse changes detected.