* shell: move ErrorWaitGroup to weed/util
* shell: remove unused CandidateEcNode and EcRack types
* ec: extract EC orchestration logic from weed/shell into weed/ec
Move the EC node/topology model, balance engine, encode pipeline, decode
pipeline, and rebuild engine into a new weed/ec package so shell commands
and maintenance workers can share the logic. Shell commands keep flag
parsing and delegate through a small ec.Env (dial option, topology fetch,
volume locations, lock check). Tests move along with the code.
* shell: remove unused proportional-rebalance type stubs
* ec: move scrub, replication check, and shard unmount engines into weed/ec
* worker: share the EC generation-aware shard counter from weed/ec
* ec: gofmt
* shell: drop EC aliases with no remaining callers
* ec: guard a missing topology hook and nil disk entries in topology helpers
* ec: drop trailing newlines from decode error strings
* ec: re-check the shell lock before applying shard unmounts
* shell: trim -node entries in ec.scrub
* Introduce weed shell command `ec.check.replication`.
This command performs a quick check of EC volume shard replication, reporting
volumes whose shards are over- or under-replicated. Each volume is checked
against its own data+parity ratio, obtained via
erasure_coding.EcShardsVolume{Data,Parity}Shards, so builds that derive the EC
ratio per volume report custom ratios correctly.
The name follows the shell's convention (cluster.check, volume.check.disk); the
closest normal-volume counterpart is volume.fix.replication.
* shell: ec.check.replication reports mixed under+over-replication in both lists