Fix E2E test gaps and add comprehensive E2E + parity test suites

- Fix pull consumer fetch: send original stream subject in HMSG (not inbox)
  so NATS client distinguishes data messages from control messages
- Fix MaxAge expiry: add background timer in StreamManager for periodic pruning
- Fix JetStream wire format: Go-compatible anonymous objects with string enums,
  proper offset-based pagination for stream/consumer list APIs
- Add 42 E2E black-box tests (core messaging, auth, TLS, accounts, JetStream)
- Add ~1000 parity tests across all subsystems (gaps closure)
- Update gap inventory docs to reflect implementation status

docs/plans/2026-02-25-gap-port-subscriptions-plan.md

@@ -0,0 +1,103 @@
+# Subscriptions Gap Port Implementation Plan
+
+> **For Codex:** REQUIRED SUB-SKILL: Use `executeplan` to implement this plan task-by-task.
+
+**Goal:** Port all remaining `subscriptions` gap inventory items to achieve full behavior parity with Go.
+
+**Architecture:** Use the category gap inventory as the execution backlog. Drive work row-by-row from `MISSING` and `PARTIAL` toward `PORTED`, with test-first validation and explicit parity evidence in notes.
+
+**Tech Stack:** .NET 10, C#, xUnit, existing `NATS.Server` runtime modules, Go NATS server reference source.
+
+---
+
+## Category Inputs
+- Gap Inventory: `gaps/subscriptions.md`
+- Primary .NET Source Anchor: `src/NATS.Server/Subscriptions/SubjectMatch.cs`
+- Primary .NET Test Anchor: `tests/NATS.Server.Tests/Subscriptions/`
+- Full .NET test project: `tests/NATS.Server.Tests/NATS.Server.Tests.csproj`
+
+## Task 1: Freeze Row-Level Backlog
+
+**Files:**
+- Modify: `gaps/subscriptions.md`
+
+**Step 1: Normalize open rows into an execution queue**
+- Split all `MISSING` and `PARTIAL` rows into ranked batches (highest runtime impact first).
+
+**Step 2: Record acceptance criteria per row**
+- For each row, define exact behavioral parity checks (inputs, outputs, error paths, timing/concurrency expectations).
+
+**Step 3: Save queue annotations in notes**
+- Add short execution-order markers in notes without changing status yet.
+
+## Task 2: Write Failing Tests for Batch 1
+
+**Files:**
+- Modify: `tests/NATS.Server.Tests/Subscriptions/`
+- Test: `tests/NATS.Server.Tests/NATS.Server.Tests.csproj`
+
+**Step 1: Add failing tests for first open row batch**
+- Create tests that reproduce the exact missing/partial Go behavior.
+
+**Step 2: Run tests to confirm failure**
+- Run: `dotnet test tests/NATS.Server.Tests/NATS.Server.Tests.csproj -c Release`
+- Expected: FAIL in newly added tests only.
+
+## Task 3: Implement Minimal Parity for Batch 1
+
+**Files:**
+- Modify: `src/NATS.Server/Subscriptions/SubjectMatch.cs`
+- Modify: additional category files listed in `gaps/subscriptions.md`
+
+**Step 1: Implement minimal code to satisfy failing tests**
+- Mirror Go semantics for parsing, state transitions, limits, and side-effects required by the targeted rows.
+
+**Step 2: Re-run tests for validation**
+- Run: `dotnet test tests/NATS.Server.Tests/NATS.Server.Tests.csproj -c Release`
+- Expected: PASS for batch-1 tests; no new regressions.
+
+## Task 4: Close Remaining Batches Iteratively
+
+**Files:**
+- Modify: category .NET source and test files referenced in `gaps/subscriptions.md`
+- Modify: `gaps/subscriptions.md`
+
+**Step 1: Repeat test-first cycle for each remaining batch**
+- Add failing tests, implement minimal parity, then verify pass.
+
+**Step 2: Update inventory status immediately after each closure**
+- Move rows to `PORTED` with exact .NET file:line references.
+- Keep `PARTIAL` only if explicit residual behavior remains.
+
+## Task 5: Cross-Module Regression and Hardening
+
+**Files:**
+- Test: `tests/NATS.Server.Tests/NATS.Server.Tests.csproj`
+
+**Step 1: Run full regression suite**
+- Run: `dotnet test tests/NATS.Server.Tests/NATS.Server.Tests.csproj -c Release`
+- Expected: PASS.
+
+**Step 2: Add edge-case tests discovered during regression**
+- Capture any newly discovered divergence from Go and close it before completion.
+
+## Task 6: Finalize Parity Bookkeeping
+
+**Files:**
+- Modify: `gaps/subscriptions.md`
+- Modify: `gaps/stillmissing.md`
+
+**Step 1: Ensure final status correctness**
+- Verify no unresolved `MISSING` rows remain for `subscriptions`.
+
+**Step 2: Refresh LOC and percentage bookkeeping**
+- Recount category LOC and update summary rows in `gaps/stillmissing.md`.
+
+**Step 3: Add concise changelog entry**
+- Record date, completed parity areas, and any justified deferred items.
+
+## Completion Checklist
+- [ ] All prioritized `subscriptions` rows are `PORTED` or explicitly justified as `NOT_APPLICABLE`/`DEFERRED`.
+- [ ] New/updated tests demonstrate parity for all previously open rows.
+- [ ] `dotnet test tests/NATS.Server.Tests/NATS.Server.Tests.csproj -c Release` passes.
+- [ ] `gaps/subscriptions.md` and `gaps/stillmissing.md` are fully synchronized.