fix(joinir): Phase 241-EX - Remove hardcoded 'sum' check from Pattern3

Remove legacy hardcoded 'sum' carrier validation that was blocking
array_filter patterns with different accumulator names (e.g., 'out').

Before: Pattern3 required carrier named 'sum' to exist
After: Pattern3 uses carrier_info generically (any carrier name works)

Test results:
- phase49_joinir_array_filter_smoke: PASS ✅
- phase49_joinir_array_filter_fallback: PASS ✅
- phase49_joinir_array_filter_ab_comparison: PASS ✅
- Full suite: 909/909 PASS, 0 FAIL

Also: Archive old roadmap documentation (67k lines moved to docs/archive/)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/archive/roadmap/phases/phase-15/imports-namespace-plan.md

@@ -0,0 +1,38 @@
+# Phase 15.3 — Imports/Namespace/nyash.toml Plan
+
+Status: 15.3 planning; focus remains on Stage‑1/2 compiler MVP. This document scopes when and how to bring `nyash.toml`/include/import/namespace into the selfhost path without destabilizing parity.
+
+Goals
+- Keep runner‑level `nyash.toml` parsing/resolution as the source of truth during 15.3.
+- Accept `using/import` syntax in the Ny compiler as a no‑op (record only) until resolution is delegated.
+- Avoid VM changes; resolution happens before codegen.
+
+Scope & Sequence (Phase 15.3)
+1) Stage‑1/2 compiler stability (primary)
+   - Ny→JSON v0 → Bridge → PyVM/llvmlite parity maintained
+   - PHI merge remains on Bridge (If/Loop)
+2) Imports/Namespace minimal acceptance (15.3‑late)
+   - Parse `using ns` / `using "path" [as alias]` as statements in the Ny compiler
+   - Do not resolve; emit no JSON entries (or emit metadata) — runner continues to strip/handle
+   - Gate via `NYASH_ENABLE_USING=1`
+3) Runner remains in charge
+   - Keep existing Rust runner’s `using` stripping + modules registry population
+   - `nyash.toml` parsing stays in Rust (Phase 15)
+
+Out of scope (Phase 15)
+- Porting `nyash.toml` parsing to Ny
+- Cross‑module codegen/linking in Ny compiler
+- Advanced include resolution / package graph
+
+Acceptance (15.3)
+- Ny compiler can lex/parse `using` forms without breaking Stage‑1/2 programs
+- Runner path (Rust) continues to resolve `using` and `nyash.toml` as before (parity unchanged)
+
+Looking ahead (MIR18 / Phase 16)
+- Evaluate moving `nyash.toml` parsing to Ny as a library box (ConfigBox)
+- Unify include/import/namespace into a single resolver pass in Ny with a small JSON side channel back to the runner
+- Keep VM unchanged; all resolution before MIR build
+
+Switches
+- `NYASH_ENABLE_USING=1` — enable `using` acceptance in Ny compiler (no resolution)
+- `NYASH_SKIP_TOML_ENV=1` — skip applying [env] in nyash.toml (existing)