cdm deploy --dry-run: rehearse publishes (and initializations) without submitting

Motivation

Once migrations land (#77), the pre-publish testing story for an initialization is "deploy to a local PPN and see" — workable, but a rehearsal mode would make publishes (especially initialization-bearing ones) far less nerve-wracking:

cdm deploy -n paseo --dry-run

Sketch

Run the real pipeline up to (but never through) submission:

• Build everything, resolve versions, compute the publish plan (what's up-to-date, what publishes, which initializations would fire and with what from).
• Dry-run the composed extrinsics against the live node (ReviveApi dry-run calls / TransactionPaymentApi estimates) instead of submitting — surfacing reverts (e.g. a failing initialization) and fee/deposit estimates without touching chain state.
• For initialization-bearing publishes: report the initialization's dry-run result explicitly (success/revert + return data decoded against the proxy/registry error tables).
• Output the same DeployTable, marked as a rehearsal.

Notes / knowns

• Node vs Bun diverge on ReviveApi.instantiate dry-runs (observed during #76 e2e work — instantiate dry-run was dropped from the harness for this reason); the dry-run path needs to pick runtimes/APIs that behave identically or document the constraint.
• Dry-running a sequence (deploy impl → publish → migration) against unmodified chain state is inherently approximate for later steps that depend on earlier ones landing; either accept per-step approximation with a caveat in the output, or investigate chopsticks-style forked-state simulation for full fidelity.

References

#77 (initializations — the main motivation), #76 (deploy pipeline, batch composition).

Start at the cdm deploy pipeline and the batch composition described in #76, then trace how DeployTable output is produced. Read the ReviveApi dry-run and TransactionPaymentApi paths, with initialization behavior from #77, and resolve the Node/Bun and sequential-state constraints. Done means a rehearsal output reports publish and initialization results, estimates, caveats, and no submitted state changes.