Fix Necromancy ETB reanimation (#640)

[rykerwilliams]

Summary

Necromancy's ETB ability ("it becomes an Aura with "...". Put target creature card from a graveyard onto the battlefield under your control and attach this enchantment to it...") was parsing via the Animate Dead-class combinator (try_parse_reanimator_aura_etb_effect), which only handles the quoted keyword-adoption clause and silently dropped the entire targeted-reanimation sentence — no TargetFilter, no zone reference, no reanimation effect node anywhere in the AST. This is exactly why #640 reports zero targetable creatures: no target-bearing effect was ever built.

Root cause: Necromancy is printed as a plain Enchantment (no Enchant keyword line), unlike Animate Dead which is cast as an Aura and targets at cast time via its printed Enchant restriction. Necromancy's reanimation target is a genuine CR 603.3d stack target chosen when its own ETB triggered ability goes on the stack — a structurally different shape that needed its own recognizer, not a parameter tweak to the existing one.

Fix

• Added try_parse_reanimator_aura_grant_etb_effect + parse_reanimator_aura_grant_etb_shape, a new whole-body, fail-closed nom recognizer for the "grant" sub-class (plain Enchantment ETB grants Aura-hood + targets its own reanimation), wired into oracle_trigger.rs's dispatch chain alongside the existing Animate Dead arm.
• Generalized the shared reanimator-Aura chain builder (build_reanimator_aura_etb_chain → build_aura_attach_chain), parameterized by a new parser-internal EnchantGrantShape enum (Swap for Animate Dead's existing RemoveKeyword+AddKeyword behavior, GrantOnly for Necromancy's AddSubtype+AddKeyword — since Necromancy has no prior Aura subtype/Enchant restriction to swap) and a root_target: TargetFilter parameter (Animate Dead keeps its existing AttachedTo reference; Necromancy gets a genuinely-parsed target).
• Corrected several 701.17a (Mill) → 701.21a (Sacrifice) CR mis-citations found in the touched functions.

A confirmed 5-card class shares a similar "becomes an Aura with X, [producer effect], attach self to result" template (Necromancy, Last Voyage of the Uncharted, Cloudform, Lightform, Rageform). This PR scopes to Necromancy; the other 4 use an unquoted restriction clause and different producer/sacrifice phrasing, so they correctly stay Unimplemented and are tracked separately for a future follow-up.

CR references

• CR 603.3d (triggered ability targets chosen when put on the stack)
• CR 608.2b (fizzle on illegal target)
• CR 608.2c (follow the reanimation instruction)
• CR 613.1d (Layer 4 type-changing — AddSubtype)
• CR 613.1f (Layer 6 ability-granting — AddKeyword)
• CR 701.3a/b (Attach)
• CR 701.21a (Sacrifice — corrects prior 701.17a Mill mis-citations)
• CR 704.5m (unattached Aura → graveyard SBA)

Verification

• cargo fmt --all — clean
• cargo clippy --all-targets -- -D warnings — clean
• New tests (parser shape test, parse_target building-block regression test, 4 runtime pipeline tests covering full reanimation+attach+SBA-survival, cross-controller reanimation, delayed sacrifice, and CR 608.2b fizzle) — all pass
• Existing Animate Dead/Dance of the Dead test suite (10 tests) — all pass unmodified, confirming the shared builder's generalization is behavior-preserving
• cargo semantic-audit/cargo coverage — not run locally (cold MTGJSON download didn't complete in this worktree); relying on CI for corpus-level signal

Closes #640

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[github-actions]

Parse changes introduced by this PR · 1 card(s), 2 signature(s) (baseline: main f2a7bafdc173)

1 card(s) · ability/ChangeZone · added: ChangeZone (enters_under=You, from=graveyard, target=in graveyard creature, to=battlefield)

Examples: Necromancy

1 card(s) · ability/remove all Enchantment subtypes, add subtype Aura, grant ability · removed: remove all Enchantment subtypes, add subtype Aura, grant ability (affects=self, duration=permanent, grants=add subtype Aura, grants=grant ability, grants=remov…

Examples: Necromancy

[matthewevans]

Approved — Necromancy now uses its ETB trigger's real graveyard-creature target.

✅ Clean

• The change extends the existing reanimator-Aura parser seam and parameterizes the shared chain for the printed-Aura and grant-Aura shapes.
• The runtime tests exercise the parser, trigger, zone change, attachment, delayed sacrifice, cross-controller target, and fizzle paths; each would fail if the new dispatch were removed.
• The Oracle text and sacrifice citation were independently checked against Scryfall and the current Comprehensive Rules.

Recommendation: approved for the merge queue.