feat(parser+engine): dynamic-cost keyword grants for Scavenge/Encore/…

[claytonlin1110]

The engine already has the building blocks for a keyword-with-cost-formula grant: ManaCost::SelfManaCost (the card's own mana cost) plus ContinuousModification::AddKeyword, used for one-shot single-target grants like Snapcaster Mage's flashback trigger. A continuous, filter-scoped variant of the same idea already existed for a subset of graveyard keywords (Flashback/Escape/Mayhem/Scavenge/Encore via GraveyardGrantedKeywordKind), but stopped short of several real cards:

1. No cost-delta support — nothing could express "equal to its mana cost reduced by {2}".
2. Graveyard-only — the combinator hard-required the affected filter to be the controller's graveyard; hand-zone grants (Foretell) weren't recognized at all.
3. Embalm was missing from GraveyardGrantedKeywordKind even though the runtime resolver already supported it.
4. can_foretell_card/foretell_cost read obj.keywords directly instead of the off-zone-aware path graveyard keywords already used, so a continuously granted Foretell on a hand card would silently never be castable.
5. No test exercised a filter-scoped (not SpecificObject) continuous grant through to activation.

Fix

• ManaCost::SelfManaCostAdjusted { delta: i32 } (types/mana.rs) — a sibling of SelfManaCost, not a field added to it (the bare marker is matched in ~20 call sites across casting/payment/restriction/AI code; keeping them distinct avoids a wire-format change to every existing granted keyword). Resolved at the single existing choke point, game::keywords::resolve_keyword_mana_cost, flooring the adjusted generic component at {0} per CR 601.2f.
• GraveyardGrantedKeywordKind::Embalm (CR 702.128a) — pure parser-recognition gap; the runtime resolver already handled it.
• Hand-zone Foretell grant (CR 702.143a/d) — a small dedicated combinator pair (try_parse_hand_foretell_grant_clause / parse_hand_foretell_continuation) mirroring the graveyard shape, reusing the already-generic FilterProp::WithoutKeywordKind for "without foretell".
• effective_foretell_cost (game/keywords.rs) — mirrors the existing effective_harmonize_cost/effective_sneak_cost family; can_foretell_card/handle_foretell now resolve through it instead of the raw battlefield-only foretell_cost.
• Fixed a latent "without foretell" bug: a bare "foretell" token fell through to Keyword::from_str, which concretizes via parse_keyword_mana_cost("") to Keyword::Foretell(ManaCost::zero()) — an exact-{0}-cost match, not a discriminant match. "foretell" now joins the existing flashback/embalm/harmonize/... discriminant-only keyword list in oracle_target.rs.
• New runtime test proving a filter-scoped (2+ matching objects, not SpecificObject) continuous grant resolves each recipient's own mana cost correctly, for both the graveyard and hand-zone paths — this exact shape was previously unproven.

Real cards unlocked

Card	Legality	Zone	Keyword	Cost formula
Varolz, the Scar-Striped	Commander/Legacy/Modern/Pioneer/Vintage	Graveyard	Scavenge	mana cost
Young Deathclaws	Commander/Legacy/Vintage	Graveyard	Scavenge	mana cost
Wire Surgeons	Commander/Legacy/Vintage	Graveyard	Encore	mana cost
Bohn, Beguiling Balladeer	Commander/Legacy/Vintage	Hand	Foretell	mana cost reduced by {2}
Dream Devourer	Modern/Pioneer/Commander/...	Hand	Foretell	mana cost reduced by {2}
Naktamun (Plane)	Planechase	Graveyard	Embalm	mana cost
The Cave of Skulls (Plane)	Planechase	Graveyard	Scavenge	mana cost
Singing Towers of Darillium (Plane)	Planechase	Hand	Foretell	mana cost reduced by {2}

Verified against data/mtgjson/AtomicCards.json (current, not the checked-in card-data.json export).

Fossilize (Sue, Everlasting Dinosaur) and Madness (Falkenrath Gorger's "isn't on the battlefield" multi-zone filter) are deliberately out of scope — Fossilize has no Comprehensive Rules entry to annotate against, and Falkenrath Gorger's zone scope is broader than hand+graveyard.

Testing

• Parser unit tests: top_level_static_embalm_grant_stays_on_graveyard_cards, top_level_static_foretell_grant_stays_on_hand_cards_with_cost_delta (parser/oracle_tests.rs).
• Runtime tests: filter_scoped_scavenge_grant_resolves_per_object_cost_for_every_match, filter_scoped_foretell_grant_is_visible_to_hand_cast_path_with_cost_delta (game/casting_tests.rs).
• cargo fmt --all clean.

Note on verification: this environment's local Rust toolchain has no working MSVC linker (verified independently of this change — even cargo new; cargo run on a trivial project fails to link), so I could not run cargo test/cargo clippy locally. I did a manual, file-by-file audit of every exhaustive match over ManaCost across the whole workspace (18 files, ~20 match sites) to add the new variant safely, and traced every call site through to its caller by hand. CI (ubuntu-latest) is the first real compile/test signal for this PR — flagging this explicitly rather than silently.

Closes #5045

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[matthewevans]

Current-head review on bd8f217a23ddd49cc194d3277cd57fb00d9b9ff8:

• Real parsed Foretell grants can recurse through effective keyword filtering. The parser preserves the without foretell affected filter, off-zone keyword collection evaluates that filter through matches_target_filter, and WithoutKeywordKind(Foretell) asks for effective keyword presence again. The runtime proof misses this production shape because it manually omits the WithoutKeywordKind filter. Please break the self-recursion for off-zone AddKeyword affected-filter evaluation and add a runtime test using the parsed Bohn/Dream Devourer static, including a card that already has Foretell.
• This is parser/engine work and there is no current coverage-parse-diff sticky yet. Please wait for/regenerate current-head parser proof before asking for approval.

[github-actions]

Parse changes introduced by this PR

✓ No card-parse changes detected.

[matthewevans]

Thanks for the update. The current head adds the recursion guard and the parse-diff sticky is now present, but the original proof gap is still open before I can clear the requested-changes state.

The previous review asked for a runtime test using the parsed Dream Devourer/Bohn-style static, including a hand card that already has printed Foretell. The current tests still do not cover that shape: dream_devourer_foretell_negatives says it covers a printed-Foretell card, but the actual fixtures are only a land and a cheap nonland. The printed-Foretell runtime coverage that exists elsewhere uses a synthetic SpecificObject remover, not the parsed without foretell affected filter that caused the recursion concern.

Please add a parsed-static runtime regression with a hand card that already has Keyword::Foretell, and assert it keeps its printed foretell cost / does not receive the Dream Devourer reduced-cost grant. That will prove the WithoutKeywordKind(Foretell) affected filter and the off-zone recursion guard work together on the production path.

[matthewevans]

Current head addresses the prior blocker. The new dream_devourer_declines_grant_for_printed_foretell_card regression uses the parsed Dream Devourer static, seeds a hand card with printed Foretell in base_keywords, and asserts the printed {5} cost wins over the possible Dream Devourer MV-2 {4} grant. That exercises the WithoutKeywordKind(Foretell) affected filter together with the off-zone recursion guard on the production path requested in the previous review. The parse-diff sticky is current for this head and reports no card-parse changes. Approving for merge queue; required checks can gate the actual merge.

[claytonlin1110]

@matthewevans Would you review this PR pleaes? it's removed from merge queue, even CI all passed