docs(research): add Agent Safehouse HN launch and Apple Container 1.0 stable

- agent-sandbox-landscape.md: update agent-safehouse star count (~1.4k →
  ~1.8k), add HN thread #47301085 link and key discussion notes (creator
  framing, Simon Willison observation, top community quote on sandboxing
  being THE major challenge), note Apple Container 1.0 stable (Jun 9 2026)
- hn-agent-safety-discourse-july-2026.md: add Agent Safehouse March 12
  launch to the sandboxing boom section as context that prefigures the
  June–July shift in community tone

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/research/hn-agent-safety-discourse-july-2026.md

@@ -43,6 +43,18 @@ surveyed what developers were actually deploying: "containers or YOLO"
 dominated. The honest community mood was that most teams hadn't solved
 this and were shipping anyway.
 
+The March 12 launch of **Agent Safehouse**
+([#47301085](https://news.ycombinator.com/item?id=47301085), 823 points)
+crystallised the community framing: a zero-dep `sandbox-exec` wrapper for
+macOS that attracted the top comment *"I honestly think that sandboxing is
+currently THE major challenge that needs to be solved for the tech to fully
+realise its potential."* The creator's own framing — "no dependencies, no
+daemons, no subscription; the simplicity is the feature" — and Simon
+Willison's observation that evaluating whether a sandboxing tool works as
+intended is itself hard, both prefigure the June–July shift in tone. See
+[`agent-sandbox-landscape.md`](agent-sandbox-landscape.md) for a full
+per-project breakdown.
+
 ## The June–July attack cascade
 
 Six attack patterns broke in quick succession. Together they form the