feat(opy): complete collection mutation and control flow

[e54-bot]

Summary

• complete del lowering for global/player variables through three dimensions
• support accepted continue, goto RULE_START, and dynamic loc+ control-flow forms
• add pinned OverPy 9.7.10 differential fixtures, diagnostics, provenance coverage, and support documentation

Validation

• cargo test -p opy-rs
• pinned-oracle differential corpus

Fixes #328

[Teakowa]

Blocking findings:

1. crates/opy-rs/src/lower/statements.rs / crates/opy-rs/src/compiler/lowering.rs — the new del depth boundary is one indexed level too strict. Pinned OverPy 9.7.10 rewrites the final deletion first, accepts a source target with four indexes through its three-dimensional reconstruction path, and only reaches Cannot delete index of 4d array when there is one additional nested __valueInArray__. This patch rejects every target with indexed_expr_depth >= 4 / indices.len() > 3, so an upstream-accepted core form is rejected while the support row is promoted to Supported. The same upstream reconstruction also explicitly rejects random outer/middle indexes; the new native path has no equivalent boundary. Add pinned acceptance/rejection probes for these nested forms and match the 9.7.10 boundary before marking del Supported.

2. crates/opy-rs/src/compiler/lowering.rs — continue still fails when a switch is nested inside an enclosing for / while / do ... while. contains_loop_continue only descends through Stmt::If; a switch falls through to lower_switch_body, which sends its statements to lower_action(..., BreakTarget::Switch), where Stmt::Continue is rejected. Pinned OverPy's continue.ts walks parents through intervening structures until it reaches the enclosing loop, so this is an established accepted nesting form. Add an oracle-backed switch-in-loop case and preserve the enclosing-loop continue semantics before promoting the row to Supported.

3. crates/opy-rs/src/compiler/lowering.rs / crates/opy-rs/src/compiler/tests/control_flow.rs — the new conditional dynamic goto loc+... path is only protected by a native-output assertion. The pinned fixture covers an unconditional dynamic goto, not if condition: goto loc+expr. This matters because loc+ is action-relative and pinned OverPy deliberately tracks variable gotos at rule scope to preserve surrounding control-flow/action positions. #328 requires independent upstream/differential evidence for completed behavior, so the implementation currently self-specifies this new path. Add a pinned 9.7.10 differential case with surrounding actions/structure and make the lowering match that action-distance behavior; do not rely on the single-Skip If assertion as completion evidence.

[Teakowa]

Follow-up: findings 2 and 3 are fixed, and the del depth/random-index cases now match the pinned oracle. One compatibility gap remains in finding 1: lower_delete checks randomness only in indices[..indices.len() - 1], but pinned OverPy 9.7.10 __del__.ts also calls astContainsRandom(content.args[0]) on the indexed array/root expression. That matters for player-variable targets because the parser permits an arbitrary player expression as the __playerVar__ receiver (for example a random player expression). A nested target such as del random.choice(getAllPlayers()).values[0][0][0] is therefore rejected upstream but is not rejected by this native guard. Include the root/player receiver in the nested-random check and add a pinned rejection probe for this form. After that, the previous review findings are otherwise resolved.

[Teakowa]

LGTM