chore(fast-inbox): single canonical path for rollup sample-input regeneration (A-1435)

[spalladino]

Deduplicates how the committed rollup protocol-circuit sample inputs (noir-projects/noir-protocol-circuits/crates/rollup-*/Prover.toml) get regenerated. Two paths previously both wrote rollup-block-root-first, rollup-block-root-first-single-tx, rollup-checkpoint-root-single-block, rollup-checkpoint-merge, and rollup-root, so the committed fixtures drifted depending on which ran last.

• Makes the prover-client regenerate_rollup_sample_inputs.test.ts suite the sole owner of every rollup circuit at or above the transaction merge: the block-root variants, block-merge, both checkpoint roots, checkpoint-merge, tx-merge, and root.
• Stops the e2e full.test.ts dump from writing the block-root and checkpoint samples it overlapped on. The e2e dump now regenerates only what needs real client-proved transactions the simulated orchestrator cannot produce: the private-kernel circuits and the transaction-base rollups (rollup-tx-base-private, rollup-tx-base-public).
• Adds a dedicated three-tx scenario to the suite to restore rollup-tx-merge coverage, which was dropped when orchestrator_single_checkpoint.test.ts was deleted and replaced by this suite. A block with three txs forces one tx-merge before the two-input block root, whereas one- or two-tx blocks feed the block root directly.
• Updates the regen docs (barretenberg/cpp/CLAUDE.md, the update-prover-toml and gate-counts skills, and the updateProtocolCircuitSampleInputs JSDoc) to the two-command split and removes the dead orchestrator_single_checkpoint.test.ts references.

Ownership after this change (each committed rollup Prover.toml has exactly one writer, no overlap):

• prover-client suite (AZTEC_GENERATE_TEST_DATA=1 yarn workspace @aztec/prover-client test regenerate_rollup_sample_inputs): the 11 block-root / block-merge / checkpoint / tx-merge / root tomls.
• e2e (AZTEC_GENERATE_TEST_DATA=1 FAKE_PROOFS=1 full.test): private-kernel circuits plus rollup-tx-base-private / rollup-tx-base-public.

Part of the Fast Inbox (AZIP-22) cleanup stack, on top of #24784..#24794.

Validation: neither regeneration path runs in this environment (the prover-client build here has stale artifacts and e2e needs a full L1/anvil stack), so the actual fixture regeneration and the downstream nargo execute checks are validated on CI. Locally verified statically that the suite's scenario dump arrays plus the e2e list exactly cover all 13 committed rollup tomls with no overlap, and that a three-tx block routes through getTxMergeRollupProof and captures rollup-tx-merge test data.

Review follow-up (phase-2 final review)

Post-flip a zero-tx non-first block carrying a bundle is a live shape routed through the msgs-only block root (wired in #24789), so the regen suite gains a per-block-distribution scenario dumping rollup-block-root-msgs-only, and the circuit joins the CI nargo execute list — the first regen run must create and commit its Prover.toml. The documented e2e regen command also moves to the file's real location (single-node/prover/server/full.test; the old e2e_prover/full.test jest pattern matches nothing).