feat: carry identifier and nested-value provenance in mapped text

[e54-bot]

Summary

Implements #328: the canonical workshop-rs/mapped-text-v1 artifact now carries the provenance surface introduced by the v1.1.0 public API (#326), so provider-generated mapped Workshop programs preserve exact identifier and nested-value source provenance across the provider boundary.

Format extension (all additive, optional members — format ID unchanged):

• rule entries: name_span, event_name_span
• action entries: identifier_span (covers Set/Modify * Variable* targets, For * Variable* targets, Assign Member, Call Subroutine callees)
• condition and action_argument entries: identifier_span plus recursive children ({span?, identifier_span?, children} aligned positionally with the public Value tree: array indices, call arguments, vector x/y/z, player-variable player child)
• All four entry kinds now accept entries without a coarse span — identifier-only provenance is real (e.g. (expr).member records an identifier span but no value span)

SourceMap::extract emits these members when recorded; SourceMap::apply validates every span and restores them onto the parsed Program. Nested children are positional: entries beyond the reparsed Value tree are dropped (emission can canonicalize value forms), missing positions stay unmapped rather than being guessed — matching Wright's rule that absent exact provenance reports unmapped.

Compatibility: old artifacts without the new members decode and apply unchanged; unknown JSON members are ignored as before. Only span-less entries require a consumer built for the extended contract — which is precisely the consumer that needs identifier provenance.

docs/source-preservation.md documents the extended members and the tolerance/compatibility semantics. ADR-0013 needs no change (it records the decision, not field-level detail).

Test plan

• cargo test -p workshop-rs --lib tests::source_map — 13/13, including authored-JSON attach, identifier-only round trips, nested-child validation, atomic rejection, backward compatibility
• cargo test --workspace --all-targets — 235 + 9 + 107 + 15 + 15, all passing; corpus extract → emit → parse → apply covers every mapped position incl. nested paths on real projects
• cargo fmt --all --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo run -p workshop-rs --bin workshop-catalog-gen -- check — DIFF-CHECK-OK
• git diff --check

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