audit: add LEP-6 foundation storage-truth scaffolding

[j-rafique]

No description provided.

[roomote-v0]

Rooviewer   See task

Reviewed the LEP-6 storage-truth foundation scaffolding. The PR is well-structured with clean proto definitions, proper KV store indexing (including secondary indices for heal ops), comprehensive query/state management, and good test coverage. Two minor items flagged:

• Placeholder msg handlers use ErrInvalidSigner for nil-request validation -- semantically misleading error code for clients
• devnet/go.sum adds a self-referential LumeraProtocol/lumera v1.10.0 checksum entry -- likely dead weight from go mod tidy

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}

[roomote-v0]

All three placeholder handlers wrap ErrInvalidSigner (error code 1) for nil-request and empty-creator checks. For the nil-request case this is semantically misleading -- a nil request is an invalid argument, not an invalid signer. Clients that match on error codes will misclassify the failure. Consider using a dedicated ErrInvalidRequest or sdkerrors.ErrInvalidRequest for the nil check, and reserving ErrInvalidSigner for the creator-specific validation.

_{Fix it with Roo Code or mention @roomote and request a fix.}

[roomote-v0]

This adds a github.com/LumeraProtocol/lumera v1.10.0/go.mod entry to devnet/go.sum, which is a self-referential dependency (the devnet module depending on its own parent repo at a tagged version). This is likely an artifact of running go mod tidy with a stale module cache or a replace directive that was temporarily removed. If the devnet module uses a replace directive to point at the local ../ path, this checksum line is dead weight and could cause confusion if the tagged version diverges from the local code. Worth confirming this entry is intentional.

_{Fix it with Roo Code or mention @roomote and request a fix.}