perf(server-ng): reach single-node latency parity with legacy server

[hubcio]

server-ng trailed the legacy server on single-node benchmarks:
the default cpu allocation collapsed all work onto one shard,
produce hashed each batch three times (convert, stamp, flush
revalidation), and a lone consumer crossing a sealed segment
degraded to full-segment scans through unbounded read handles.

Shard allocation now defaults to numa:auto. Produce computes
the batch checksum once and marks locally originated batches
trusted; replicated blobs keep a per-message receive gate on
followers, so transit integrity still holds end to end. Sealed
segment read handles are capped by a per-partition LRU.

Consumer groups on the ng metadata plane gain legacy-parity
error semantics: join/leave against a missing stream, topic or
group fail loudly (1009/2010/5000), leaving as an absent member
returns 5006 instead of silent success, and the wire codes are
pinned by an integration test across TCP, QUIC and WebSocket.
The HTTP listener now binds from the cluster roster port, so
one-host clusters run from byte-identical per-node configs.

[codecov]

Codecov Report

❌ Patch coverage is 90.27778% with 98 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.31%. Comparing base (d9635b6) to head (7bf57b2).

Files with missing lines	Patch %	Lines
core/server_common/src/send_messages2.rs	94.07%	12 Missing and 14 partials ⚠️
core/partitions/src/iggy_partition.rs	85.98%	17 Missing and 5 partials ⚠️
core/server-ng/src/bootstrap.rs	79.71%	13 Missing and 1 partial ⚠️
core/partitions/src/poll_plan.rs	83.05%	6 Missing and 4 partials ⚠️
core/metadata/src/stm/stream.rs	10.00%	9 Missing ⚠️
core/partitions/src/log.rs	94.56%	4 Missing and 1 partial ⚠️
core/metadata/src/stm/consumer_group.rs	96.89%	4 Missing ⚠️
core/partitions/src/iggy_index_reader.rs	80.00%	1 Missing and 3 partials ⚠️
core/metadata/src/stm/result.rs	88.88%	2 Missing ⚠️
core/partitions/src/iggy_partitions.rs	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             master    #3746       +/-   ##
=============================================
- Coverage     74.53%   61.31%   -13.23%     
  Complexity      969      969               
=============================================
  Files          1306     1305        -1     
  Lines        150028   139603    -10425     
  Branches     125462   115111    -10351     
=============================================
- Hits         111829    85594    -26235     
- Misses        34700    50366    +15666     
- Partials       3499     3643      +144     

Components	Coverage Δ
Rust Core	58.71% <90.27%> (-16.13%)	⬇️
Java SDK	62.71% <ø> (ø)
C# SDK	71.14% <ø> (-1.13%)	⬇️
Python SDK	92.27% <ø> (ø)
PHP SDK	84.52% <ø> (ø)
Node SDK	92.24% <ø> (ø)
Go SDK	43.08% <ø> (ø)

Files with missing lines	Coverage Δ
core/journal/src/prepare_journal.rs	88.67% <ø> (ø)
core/metadata/src/stm/snapshot.rs	86.30% <100.00%> (ø)
core/partitions/src/journal.rs	77.77% <100.00%> (ø)
core/server-ng/src/dispatch.rs	33.38% <ø> (ø)
core/server-ng/src/partition_reconciler.rs	86.31% <100.00%> (ø)
core/server-ng/src/responses.rs	39.76% <ø> (ø)
core/simulator/src/client.rs	57.05% <ø> (ø)
core/metadata/src/stm/result.rs	92.03% <88.88%> (-0.31%)	⬇️
core/partitions/src/iggy_partitions.rs	69.76% <33.33%> (-0.34%)	⬇️
core/metadata/src/stm/consumer_group.rs	68.08% <96.89%> (+10.15%)	⬆️
... and 7 more

... and 252 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.