Add architecture review findings and address documentation issues

Review of all ADR documents (001-007) and peripheral architecture docs
identified 3 critical, 10 warning, and 7 suggestion issues.

Addressed in this commit:
- W-1: Add draft qualifier to ADR-002 reference to incremental exploration
- W-2: Add Alternatives Considered section to ADR-001
- W-3: Add Document Lifecycle section to README.md (draft/stable/deprecated)
- W-4: Clarify includeCompleted semantics (only 'completed' status triggers exclusion)
- W-5: Document file I/O runtime constraints in frontmatter.md
- W-6: Add ADR reference to architecture.md redirect
- W-7: Verify CVE-2025-64718 (confirmed real, improved description)
- W-9: Convert workspace-absolute paths to relative/monorepo references
- S-7: Add future ADR-008 note to incremental-update-exploration.md

Critical issues (C-1, C-2, C-3) and remaining warnings (W-8, W-10, S-4, S-5)
were addressed by a parallel agent in a prior commit.

All 16 review tasks created and resolved.

tasks/architecture/w-5-fileio-runtime-portability.md

@@ -0,0 +1,22 @@
+---
+id: architecture/w-5-fileio-runtime-portability
+name: Document file I/O function runtime constraints and export path
+status: completed
+depends_on:
+  - architecture/w-4-taskstatus-enum-values
+created: 2026-04-26T09:10:51.293468161Z
+modified: 2026-04-26T09:10:51.293468694Z
+scope: narrow
+risk: medium
+---
+
+# Description
+
+**Review ref**: W-5 (Warning)
+**Files affected**: `docs/architecture/frontmatter.md`, `docs/architecture/build-distribution.md`
+
+`parseTaskFile` and `parseTaskDirectory` are async and use Node.js `fs` APIs, but ADR-001 and build-distribution.md state the library works in Node, Deno, and Bun. Document whether these I/O functions are available in all runtimes. Consider a separate export path (e.g., `@alkdev/taskgraph/fs`) for file I/O to avoid bundling Node APIs into Deno/Bun consumers.
+
+Depends on W-4 (TaskStatus definition) only if the file I/O discussion touches file-level defaults for status fields.
+
+**Source**: `/docs/reviews/architecture-review-2026-04-26.md` W-5