docs(gep): retrofit GEP-16 (wake-path) + GEP-17 (cross-OS research)

GEP-16 captures the seven boundary-glue layers between GEP-5 (bwrap) and
GEP-8 (dispatcher) that v0.0.3 actually needed for end-to-end agent
wake — path math, sibling-dir creation, CLI binary auto-mount,
auth_binds schema extension, env rewriting, stdout fallback, and the
director wake PubSub topic. Extends GEP-5 + GEP-8 (bidirectional
frontmatter links added).

GEP-17 is pure research — the cross-OS sandbox (bwrap alternatives on
macOS/Windows) + filesystem-watcher landscape. No decisions, no
roadmap commitments. Answers "is a Mac/Windows port large or small?"
in advance of anyone asking.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: foobarto

docs/geps/0005-sandboxing-bwrap-then-podman.md

@@ -8,6 +8,7 @@ created: 2026-04-17
 implemented-in: v0.0.1
 requires: [2]
 see-also: [3, 4, 9, 12]
+extended-by: [16]
 history:
   - date: 2026-04-17
     status: Draft

docs/geps/0008-provider-registry-and-auto-detect.md

@@ -9,6 +9,7 @@ updated: 2026-04-17
 implemented-in: v0.0.3
 requires: [2, 4]
 see-also: [3, 5]
+extended-by: [16]
 history:
   - date: 2026-04-17
     status: Draft