jagged: direct concat for prefix-aligned points

[hero78119]

Problem

Jagged PCS previously handled suffix-aligned evaluation points by padding each column polynomial to a power-of-two height and bit-reversing rows before concatenation. Now that callers support prefix-aligned evaluation points directly, that workaround is unnecessary and adds extra zero slots/work.

Approach

• Remove per-polynomial padded-height blocks from jagged_commit; cumulative heights now use each RMM's real row count.
• Remove row bit-reversal from the commit path and directly concatenate transposed RMM columns into q'.
• Use prefix-aligned row points throughout open/verify: polynomial i is evaluated at point[..s_i].
• Update jagged docs, sumcheck wording, tests, and benches to match direct concatenation semantics.
• Add non-power-of-two height coverage to ensure real heights are committed and opened correctly.

Testing

• cargo fmt --all
• cargo test -p mpcs jagged::tests --lib — 12 passed
• cargo check -p mpcs --benches — passed; existing unrelated warning remains in crates/mpcs/benches/interpolate.rs

Risk / Rollout

Protocol semantics change from suffix-aligned bit-reversed storage to prefix-aligned direct storage. Prover and verifier paths were updated together, and tests cover power-of-two, non-power-of-two, reshape, and soundness cases. Rollback is isolated to the jagged commit/open/verify changes in this PR.

Copilot Reviewer Directive (keep this section)

When Copilot reviews this PR, apply .github/copilot-instructions.md strictly.

• Perform review only; do not commit/push/propose code changes.
• Prefer inline comments on changed lines for each actionable finding.
• If inline comments are unavailable, use [severity] path:line (symbol) format.
• Prioritize soundness, performance, and architecture risks over style.
• Output order: findings by severity, then open questions, then brief summary.
• If PR description is empty or missing key context, report PR metadata: description as a finding.