docs(validity): document predicate limit and unspecified behaviors

[youssefea]

What changed? Why?

Adds a Limits section to the Validity Transaction RPC page. It documents the default 64-predicate-per-transaction limit as a version-qualified implementation default, links to the existing expiry rules, and states that the docs do not yet specify a storage-read cost for storage predicates or propagation to other nodes.

Closes knowledge gap gap-20261005-validity-transactions-predicate-limits-propagati: "For base_sendRawTransactionValidity, what are the limits on number of predicates per transaction and storage-read cost, do validity transactions stay sequencer-local or propagate to other nodes, and what are the stable JSON-RPC error codes?"

• Gaps log: https://bdocs.cbhq.net/d/base-knowledge-gaps-log
• Linear: DEVREL-859

Notes to reviewers

Primary sources:

• 64-predicate default: DEFAULT_MAX_VALIDITY_PREDICATES = 64 in crates/execution/txpool/src/validity.rs @ v1.4.2 (same value on main); enforced via validate_batch in crates/execution/txpool-rpc/src/rpc.rs @ v1.4.2.
• Mandatory block_number expiry: same rpc.rs (validate_block_expiry_bounds / validate_has_block_expiry); already documented on fees-ordering-and-lifecycle.mdx.
• No storage-read cost or peer propagation behavior is documented in the reviewed sources; rpc.rs forwards accepted transactions to builders, which does not establish peer propagation. The page therefore says the docs do not yet specify these.
• Error codes: unchanged. The page still says codes and messages are not yet stable.

Needs owner confirmation before merge (Base protocol / node team owning base_sendRawTransactionValidity):

• Whether the production sequencer runs with the default 64-predicate limit (it is a configurable default).
• Whether there is a storage-read budget, and whether validity transactions stay sequencer-local, so these can be documented instead of flagged as unspecified.
• Whether stable error codes can be published.

How has it been tested?

• node scripts/lint-mdx.js --files-from=<changed files>: 0 errors (1 pre-existing warning on the request example code block).
• node scripts/validate-docs-structure.js: only pre-existing redirect errors for /upgrades/denim/eip-8130, unrelated to this change.
• Internal link /specifications/build-transaction/fees-ordering-and-lifecycle exists in docs/docs.json; the GitHub link returns 200.

Screenshots

N/A (text-only change)

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[linear]

DEVREL-859

[cb-heimdall]

🟡 Heimdall Review Status

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