feat(grpc): close api gap — 39 new rpcs

[kacy]

summary

closes the gap between the resp3 engine (~170 commands) and the grpc service (68 rpcs). adds 39 new rpcs, ~35 new message types, extends the pipeline streaming handler, and adds five new pipeline result types.

new commands by category:

• strings: getdel, getex, getrange, setrange
• keys: copy, randomkey, touch
• lists: lindex, lset, ltrim, linsert, lrem, lpos, lmove
• sets: sunion, sinter, sdiff, sunionstore, sinterstore, sdiffstore, srandmember, spop, smismember
• hashes: hscan
• sorted sets: zrevrank, zrevrange, zcount, zincrby, zrangebyscore, zrevrangebyscore, zpopmin, zpopmax, zdiff, zinter, zunion, zscan
• scans: sscan
• server: time, lastsave

new pipeline result types (tags 30–34): BoolArrayResponse, HScanResponse, ZScanResponse, SScanResponse, TimeResponse. pipeline oneof command extended to tag 111.

intentionally skipped: blpop/brpop (blocking doesn't map to unary grpc), multi/exec (requires stateful streaming), cluster/acl/config (admin tier), auth/quit/client (connection-level).

what was tested

• cargo build -p ember-server --features grpc — clean, zero warnings
• cargo test -p ember-server --features grpc — 137 tests, all pass
• score bound parsing verified: -inf, +inf, (5.0, 5.0 round-trip correctly through parse_score_bound()

design considerations

same-shard requirement for multi-key ops — copy, lmove, sunion/sinter/sdiff, and zdiff/zinter/zunion all route to a single shard. copy and lmove return an error when source and destination hash to different shards (same behavior as rename). the set/sorted-set multi-key ops route to the first key's shard, consistent with the resp3 handler.

with_scores on sorted set range ops — zdiff, zinter, zunion, zrangebyscore, zrevrangebyscore, and zrevrange always fetch scored data from the engine. if with_scores is false, scores are zeroed in the response rather than requiring a separate engine call.

lpos returns OptionalIntResponse — returns only the first match. a future lpos_all rpc can return an array if needed; the count field is accepted but only the first result is surfaced.