refactor(server): split responses.rs by role and unify reply framing

[hubcio]

responses.rs mixed three concerns in 2459 lines: identifier and
namespace resolution, reply frame building, and the process probe
behind GetStats. Around it the read side carried two more forks:
private server copies of the metadata crate's stream and topic
resolvers, and five hand-written ReplyHeader echo literals plus a
sixth writing the rejection result section against a private 12-byte
constant. Any change to an echo or a resolver had to be repeated at
every copy.

Split responses.rs into leaf modules by role: namespace.rs resolves
wire identifiers and partition namespaces and owns the
consumer-group offset fence, reply_frame.rs owns the seven frame
builders, and sysinfo_probe.rs owns that probe. The catalog keeps
NonReplicatedResponse and imports the three one way, keeping the
module graph a DAG.

Export StreamsInner::resolve_stream_id and resolve_topic_id beside
the sibling UsersInner::resolve_user_id, and delete the server
copies, so the in-apply, dispatch read and HTTP read gates end on
one resolution.

Give ReplyHeader two constructors: from_prepare reproduces the
committed-reply literal, echoing is the base the request-echo sites
consume with ... echoing leaves client zero on purpose: dispatch
stamps the transport id, the rest the VSR id, so no base can pick
one. The rejection section moves beside its decoder as
write_rejection_section. The NoAck fast path keeps its literal: it
stamps live consensus fields, not the echo. Frames match byte for
byte before and after.

The dispatch failure exits trade byte snapshots, which pinned the
previous refactor rather than the wire contract, for one shape test
per exit.

[codecov]

Codecov Report

❌ Patch coverage is 95.38067% with 54 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.08%. Comparing base (c2bd0c0) to head (a9c2a53).

Files with missing lines	Patch %	Lines
core/server/src/namespace.rs	88.25%	22 Missing and 7 partials ⚠️
core/server/src/reply_frame.rs	96.37%	6 Missing and 14 partials ⚠️
core/server/src/sysinfo_probe.rs	92.30%	0 Missing and 4 partials ⚠️
core/server/src/http/reads.rs	88.88%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #4089      +/-   ##
============================================
- Coverage     87.13%   87.08%   -0.05%     
  Complexity     1455     1455              
============================================
  Files          1273     1276       +3     
  Lines        215301   215145     -156     
  Branches     179909   179753     -156     
============================================
- Hits         187597   187358     -239     
- Misses        23178    23245      +67     
- Partials       4526     4542      +16     

Components	Coverage Δ
Rust Core	88.10% <95.38%> (-0.06%)	⬇️
Java SDK	67.58% <ø> (ø)
C# SDK	77.16% <ø> (+0.04%)	⬆️
Python SDK	90.97% <ø> (ø)
PHP SDK	85.67% <ø> (ø)
Node SDK	96.24% <ø> (-0.03%)	⬇️
Go SDK	69.48% <ø> (+0.03%)	⬆️

Files with missing lines	Coverage Δ
core/binary_protocol/src/consensus/header.rs	83.37% <100.00%> (+1.50%)	⬆️
core/binary_protocol/src/consensus/reply_result.rs	100.00% <100.00%> (ø)
core/consensus/src/plane_helpers.rs	95.16% <100.00%> (-0.15%)	⬇️
core/metadata/src/stm/result.rs	98.75% <100.00%> (-0.03%)	⬇️
core/metadata/src/stm/stream.rs	94.04% <100.00%> (-0.01%)	⬇️
core/metadata/src/stm/user.rs	93.16% <ø> (ø)
core/server/src/boot/mod.rs	87.19% <100.00%> (ø)
core/server/src/consumer_group.rs	97.74% <ø> (ø)
core/server/src/dispatch/authz.rs	98.40% <100.00%> (ø)
core/server/src/dispatch/failure.rs	97.56% <100.00%> (+0.19%)	⬆️
... and 14 more

... and 49 files with indirect coverage changes

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