feat: support process-to-process pushes via arweave-scheduler@1.0

[charmful0x]

this PR teaches schedulers to advertise their required codec on 422, and push@1.0 to retry generically with it:

• legacy scheduler@1.0 (ao.TN.1) requires ans104@1.0 -- (ao.N.1 case remains as-is)
• arweave-scheduler@1.0 requires tx@1.0

for tx@1.0, push reuses the target process authority selection, fetches the target-aware L1 price and anchor through arweave@2.9, signs a data-free L1 tx, and posts it through the scheduler

preserves the existing httpsig@1.0 -> ans104@1.0 fallback, from-* provenance, redirects, and security policy. accepted L1 submissions return as pending (202)

live L1 probe:

• 5CVU user -> P1: a0qln7wLeBtVb7y9TaJ7NSDHVSYKsztIkVaqdorppmY
• P1 -> P2, signed by vZY2XY authority: 0zVfrxEbxNTiWS_l-FfiRkewfLHAMdOrxy63yczzCKk
• P2 indexed and computed slot 3
• from-process=P1
• missing scheduler is omitted