[Server][DynamicAdmission] Add atomic runtime enable/disable control

[SunSi12138]

Implements #329 as a stacked change on #328.

Stack base (latest reviewed #328 exact head): 21a3ebef8e05b97dffd49cc13c5cf1209153d657
Base branch: issue-324-admission-state-kernel
Final implementation head: c1c68580e3337bf640c5c677cce829cae592f423

Scope:

• add Server-package public runtime enable/disable extension methods without introducing Abstractions -> Server dependency
• centralize publication/lifecycle writer behavior for public control and existing test publication seams
• preserve request capture, retire/reclaim, compatible stable-kernel state, and ResourceGovernor independence
• add deterministic transaction/race/request-lifecycle coverage
• document supported runtime transitions and semantics

This PR intentionally does not add enabled-to-enabled policy updates, resize/migration APIs, dynamic module redesign, Hosting/IOptionsMonitor integration, or ResourceGovernor changes.

#329 DoD / test matrix

Covered by deterministic unit/integration tests and the existing regression suite:

• public Enable from initially disabled; next-capture boundary; pre-Enable disabled capture remains bypass; unsupported server surface; caller-options isolation
• public Disable; next requests bypass; active and queued old generation continues; one-way/two-way old queue behavior; idempotent Disable; eventual reclaim
• compatible Disable -> re-enable overlap for concurrency, queue accounting, rate state and partition state without duplicate kernel registry state
• transactional configure/validation/resolution failures and partial-construction rollback
• already-enabled Enable rejection and losing concurrent Enable reclaim
• deterministic two-Enable, Enable-vs-Disable, Disable-vs-Stop, and candidate-built-vs-Stop writer races
• repeated enable/disable lifecycle boundedness and no queue/permit underflow
• Stop seal prevents later publication and final kernel diagnostics drain to zero
• runtime-disabled Admission remains independent from call capacity / ResourceGovernor
• capacity-rejected compressed requests keep zero decompression before capacity admission
• pre-admission stream accounting remains correct across Disable with an old queued generation and rejection leaves the connection reusable
• existing refactor(server): extract admission state kernel lifecycle #328 AdmissionStateKernel, feat(server): capture admission program generation per request #323 generation-capture, Admission concurrency/queue/rate/partition, and feat(server): budget pre-admission stream buffers in ResourceGovernor #319 pre-admission stream suites remain green

Lifecycle tests assert terminal stable-kernel diagnostics return to zero where applicable: LiveProgramCount=0, RetiredProgramCount=0, RuleStateCount=0, PartitionStateCount=0, QueuedCalls=0, QueuedBytes=0, ActivePermits=0.

Exact-head GitHub Actions evidence

PR Quick run: 32692486306 — success.
PR head: c1c68580e3337bf640c5c677cce829cae592f423.
Actions checkout merge: b07fe7cf1686815834c1386535d662c4391805e0 = final PR head merged onto fixed stacked base 21a3ebef8e05b97dffd49cc13c5cf1209153d657.

• Formatting: pass
• Debug build: pass, 0 warnings / 0 errors
• Release build: pass, 0 warnings / 0 errors
• Generated assembly dependency verification: pass
• Unit Tests: 1,134 passed / 0 failed / 0 skipped
• Generator Tests: 134 passed / 0 failed / 0 skipped
• Load Test Tests: 60 passed / 0 failed / 0 skipped
• Integration Tests: 394 passed / 0 failed / 0 skipped
• Total managed test cases in PR Quick: 1,722 passed / 0 failed / 0 skipped
• NativeAOT transport/topology/pre-credit smokes: pass
• Pack + package metadata/symbol/dependency checks: pass
• Package smoke: pass
• Oneway demo: pass
• Load smoke: pass; c=1 18,460.93 qps, c=4 75,071.27 qps, 0 failures
• Chaos smoke: pass; 763,672 successes, 162,717 injected faults, 0 unexpected, 0 client/server errors, 0 unobserved; retained memory 1,490,960 -> 1,054,688 (-29.26%)

All execution and testing for this implementation was performed through GitHub Actions as requested.

Ready for review. Do not merge automatically; this PR remains stacked on #328.

[SunSi12138]

Reviewed exact head c1c68580e3337bf640c5c677cce829cae592f423 against #329/#264 and the reviewed #328 base. No remaining P1/P2 found in this runtime enable/disable slice. Candidate build/publication is transactional and linearizable; losing Enable/Stop races retire unpublished candidates; Disable preserves captured queued/active generations; compatible disable→re-enable overlap reuses the stable kernel without splitting queue/concurrency/rate/partition state; ResourceGovernor/pre-admission ownership remains independent. Exact-head PR Quick 32692486306 is green, including Unit 1134/1134 and Integration 394/394.