SIG-746: rename SignalsPositionStorage zombies to OZ pattern

[worjs]

Context

SIG-746. SignalsPositionStorage.sol keeps four legacy mappings as zombies on slots 3-6 to preserve UUPS proxy storage layout. Their previous form used freeform // @deprecated line comments and retained semantic names (_marketTokenList, _positionMarketIndex, _ownerTokenList, _positionOwnerIndex), which is not the OpenZeppelin upgrade-safe pattern that auditors and the OZ upgrades plugin recognize for an intentional rename.

This change converts those four declarations to the OZ-standard rename pattern and regenerates the committed storage snapshot.

Decisions

• Renamed each retained zombie mapping to __deprecated_slot_<N> matching its current slot index, and added a /// @custom:oz-renamed-from <oldName> NatSpec line directly above each declaration. Slot index, mapping type, internal visibility, declaration order, and the trailing uint256[48] __gap are unchanged.
• Used one NatSpec annotation per variable on the line immediately above the declaration. The repo's storage diff tooling matches @custom:oz-renamed-from against the renamed variable's AST documentation node, so co-locating the annotation with the variable is what the tool actually consumes.
• Old names are preserved only inside the annotation. The new label encodes the slot number, which is the invariant that matters for a label-only rename of an unused mapping.
• Did not modify any test files. SIG-743 already provides the storage layout diff harness used to validate this rename, and the PM plan for SIG-746 explicitly excluded test changes. Verification is via the existing storage-diff path (STORAGE_STRICT_BASE=1 yarn storage:check against origin/main) plus forge inspect ... storageLayout.
• Regenerated storage-snapshots/SignalsPosition.json because the snapshot is committed and the four label fields move with the rename. AST IDs and the compiler-generated t_struct(Position)<id>_storage type identifier also shift, since the snapshot is produced from a fresh build of the full contract tree.

Risk Areas

• contracts/position/SignalsPositionStorage.sol is the storage parent of the live SignalsPosition UUPS proxy. Any change to slot index, type, offset, or order on slots 0-6 or to __gap[48] would corrupt every existing position. Reviewers should confirm slots 3-6 still hold the same mapping types and that slot 0 (core), slot 1 (_nextId), slot 2 (_positions), and slot 7 onward (__gap) are untouched.
• storage-snapshots/SignalsPosition.json is the artifact compared by yarn storage:check. The diff includes label changes on slots 3-6 plus AST ID and t_struct(Position)<id>_storage identifier renumbering. Reviewers should confirm slot, offset, and storage-type semantics on every entry are preserved and that no entry was added or removed.
• The @custom:oz-renamed-from annotation is what the OZ upgrades plugin and the in-repo storage diff tool use to authorize a label-only rename. Each annotation must point to the exact prior identifier, since a typo there would cause future upgrade-safety checks to flag the slot as a removed variable.

[signals-reviewer]

Summary

Renames four zombie storage mappings in SignalsPositionStorage.sol (slots 3-6) from their legacy semantic names to __deprecated_slot_<N>, replacing freeform // @deprecated comments with /// @custom:oz-renamed-from <oldName> NatSpec annotations. Regenerates the committed SignalsPosition.json snapshot to reflect the new labels.

Cross-PR Context

Recent Review Patterns

• PR#75 (SIG-743, storage layout CI tooling): the reviewed tooling is the infrastructure that validates this rename. That PR's comparator is what consumes the @custom:oz-renamed-from annotations added here. No issues from PR#75 carry over.

Sibling PRs (SIG-746)

• Only this PR. No cross-repo impact: the change is limited to storage variable labels with no ABI, event, or function signature modifications. Impact map confirms no downstream updates needed in v1-subgraph, v1-sdk, v1-server, or signals-app.

Issues

No issues found.

Verification performed:

• Slot integrity: Confirmed slots 0-7 preserve identical slot index, offset, and storage type between base and PR snapshots. Only the label field changed on slots 3-6.
• Mapping types preserved: uint256 => uint256[], uint256 => uint256, address => uint256[], uint256 => uint256 match exactly.
• Annotation correctness: Each @custom:oz-renamed-from references the exact prior identifier (_marketTokenList, _positionMarketIndex, _ownerTokenList, _positionOwnerIndex). The annotations are placed as /// NatSpec directly above each declaration, which compiles into the AST documentation field that BuildInfoAnnotationResolver.hasRenameAnnotation() reads.
• No stale references: Grepped the full codebase for the old variable names; they appear only in the base branch declarations (not called or accessed anywhere in contract logic).
• __gap[48] unchanged: Gap array at slot 7 is untouched in both size and position.
• Snapshot diff semantics: AST IDs and t_struct(Position)NNNN_storage type identifiers changed (expected from fresh build output). No entries added or removed. Slot, offset, and type semantics are preserved across all 8 storage entries and all 5 struct members.
• No other zombies: SignalsCoreStorage.sol and SignalsLPShare.sol have no deprecated mappings requiring similar treatment.
• Test coverage: The existing storage layout comparator tests (23 tests in storage-layout.test.ts) cover rename annotation validation, including positive and negative cases for @custom:oz-renamed-from.

Suggestions

None.

Verdict

APPROVE