Phase 3: Reduce server.New to wrapper + config split

[tgrunnagle]

Description

Land the structural payoff of the vMCP domain/transport split: split the in-memory
server.Config into a core Config + a transport ServerConfig (via
deriveCoreConfig/deriveServerConfig), then reduce server.New's body to the
thin wrapper Serve(ctx, New(deriveCoreConfig(cfg)), deriveServerConfig(cfg)) —
removing both //nolint:gocyclo as the god-object dismantles. This story maps to
RFC Phase 3 and is the only phase that touches server.New's body; the
7-param signature and observable behavior stay byte-for-byte stable while the
implementation behind them collapses onto the New/Serve seam built in Phases 1–2.

Context

See RFC THV-0076: vMCP Core Interface
for full design details. Part of the vMCP interface refactor (epic #5419).

By the time this story runs, Phase 1 has produced the VMCP interface +
New(cfg) -> VMCP core (with the admission and elicitation seams) and Phase 2 has
produced Serve(ctx, VMCP, *ServerConfig) -> *Server with all transport concerns
(mcp-go server, SDK hooks, two-phase session creation, the full middleware chain,
AS runner, status reporter, optimizer, health monitor) already re-homed under it —
but Serve is not yet called by server.New. This story closes that loop. Per
architecture.md ("PR-Sized Decomposition Guidance → Phase 3" and "Key Files to
Modify"), the work is the config decomposition plus the wrapper reduction at
pkg/vmcp/server/server.go:301.

The config split is not a clean partition (R3): per architecture.md
"Constraints", the cross-cutting fields TelemetryProvider, AuditConfig, and the
health view are consumed on both sides (the core decorates the backend client
with telemetry and runs the workflow auditor; the transport adds telemetry/audit
middleware and lifecycles the health monitor). The health monitor is built at the
composition root (A2): because New runs before Serve, the wrapper builds it once,
injects its StatusProvider into New, and hands the built *health.Monitor to Serve.
ServerConfig carries no AuthzMiddleware (authz lives in the core admission seam);
the AuthzMiddleware field on server.Config is kept vestigial — cli/serve.go
sets it and stays unchanged — and only the dead HTTP authz/annotation blocks (plus the
discovery middleware/seam) are deleted in #5445 once the legacy path is gone. This is an
in-memory-only change:
vmcpconfig.Config, the CRD/YAML model, and the wire/storage format are unchanged
inputs to New.

This phase is small but high-stakes: it is gated by the full behavioral-parity
suite (driving the stable server.New wrapper) plus the unchanged
thv vmcp serve E2E suite — the only safety net proving the reimplemented body is
observably identical.

RFC Phase(s): Phase 3
Dependencies: #5431

Scope

In scope

• Split the in-memory-only server.Config (server.go:92-185) into the core
  Config (collaborators + workflowDefs + Authz for the admission seam +
  cross-cutting TelemetryProvider/AuditConfig) and a transport-only
  ServerConfig, exposed via deriveCoreConfig(cfg, …) and deriveServerConfig(cfg)
  (P3.1 deriveCoreConfig/deriveServerConfig config split #5444).
• Pass the cross-cutting fields (TelemetryProvider, AuditConfig) to both New
  and Serve (R3 — not a clean partition); build the health monitor at the composition
  root and thread its StatusProvider into New + the built *Monitor into Serve
  (A2). ServerConfig omits AuthzMiddleware; the field on server.Config is kept
  vestigial (cli/serve.go unchanged) (P3.1 deriveCoreConfig/deriveServerConfig config split #5444).
• Reduce server.New's body to
  Serve(ctx, New(deriveCoreConfig(cfg, …)), deriveServerConfig(cfg, healthMon)), keeping
  the 7-param signature byte-for-byte unchanged, and remove both //nolint:gocyclo
  (New @300, Start @682). With the legacy path now gone, complete the A1-deferred
  cleanup: delete the now-dead authz/annotation HTTP blocks and retire the discovery
  middleware/seam + its s.core == nil guard (keeping convertAnnotations and the
  vestigial AuthzMiddleware field). Highest-integration-risk PR; likely splits (P3.2 Reduce server.New body to the wrapper #5445).

Out of scope

• Defining or moving any transport concern under Serve, or the VMCP/New core
  itself — all of that lands in Phase 1: VMCP interface, core constructor, admission + elicitation seams #5430 (Phase 1) and Phase 2: Serve transport helper, re-home transport, replace discovery #5431 (Phase 2);
  this story only derives configs and wires the existing New/Serve together.
• Any change to server.New's signature — it is stable throughout the epic; only
  the body is reimplemented.
• Any change to pkg/vmcp/cli/serve.go (the composition root) — it must require
  no changes and keep calling vmcpserver.New(...) as today.
• Any change to the CRD / YAML model or the vmcpconfig.Config loaders / wire /
  storage format — the split is in-memory only.
• Docs (docs/arch/vmcp-library.md, pkg/vmcp/doc.go) and the runnable decorator
  example — Phase 4: Documentation + runnable decorator example #5433 (Phase 4).

Child Tasks

PR-sized tasks under this story (each ≤ 400 LOC, ≤ 10 files changed excluding
tests/docs/generated, one logical change):

• P3.1 deriveCoreConfig/deriveServerConfig config split #5444: P3.1 deriveCoreConfig/deriveServerConfig config split
• P3.2 Reduce server.New body to the wrapper #5445: P3.2 Reduce server.New body to the wrapper

Acceptance Criteria

• All child tasks complete and merged
• server.New's 7-param signature and observable behavior are unchanged
  (byte-for-byte signature; clients/embedders see no behavioral difference)
• deriveCoreConfig/deriveServerConfig derive the core Config and the
  transport ServerConfig from the existing in-memory server.Config, with the
  cross-cutting TelemetryProvider/AuditConfig passed to both sides, the health
  monitor built at the composition root and threaded both ways (A2), and ServerConfig
  omitting AuthzMiddleware (the server.Config field is kept vestigial; cli/serve.go
  unchanged) (R3)
• server.New's body is reduced to
  Serve(ctx, New(deriveCoreConfig(cfg, …)), deriveServerConfig(cfg, healthMon)), both
  //nolint:gocyclo (New @300, Start @682) are removed with lint clean, and the
  A1-deferred cleanup is completed (dead authz/annotation blocks + discovery middleware/seam
  deleted; convertAnnotations and the vestigial AuthzMiddleware field retained)
• pkg/vmcp/cli/serve.go is unchanged; no in-repo caller (nor the external
  brood-box embedder) requires any change
• No serialized / wire / CRD / YAML / storage format change — the split is
  in-memory only and vmcpconfig.Config is an unchanged input to New
• Acceptance gate: the full behavioral-parity suite (tools/list,
  tools/call, resources, prompts, composite workflows, session lifecycle, cross-pod
  Redis paths) passes equivalently before/after, and the existing thv vmcp serve
  E2E suite passes unchanged

References

• RFC THV-0076 (link above)
• Epic: vMCP interface refactor #5419