docs: replace stale bash-first framing with Python-stdlib-first

The project started life as bash scripts and got rewritten to Python
(documented in docs/research/bash-vs-python-vs-go.md). Several docs
still carried the old "bash-first" framing — misleading for anyone
reading them now (8.7k lines of Python vs. ~130 lines of bash, all
in scripts/demo*.sh).

- CLAUDE.md "What this is" + "Conventions": orchestrator is Python,
  posture is stdlib-first.
- docs/prds/0010-cred-proxy.md, docs/research/manifest-format-and-
  grouping.md: quoted CLAUDE.md's old wording — re-quote.
- docs/research/built-in-supervisor-design.md, landscape-containerized-
  claude.md, agent-sandbox-landscape.md, pipelock-assessment.md,
  network-egress-guard.md: drop "bash-first" claims about the project,
  keep accurate descriptions of external tools' bash usage.

Leaves untouched: bash code-fence syntax in examples, README's
literal `bash scripts/demo.sh` invocation (the demo IS bash),
Claude Code's "Bash tool" references, IVIJL/devbox bash description
(that project actually is bash), and the bash-vs-python-vs-go
research note that records the rewrite decision.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

docs/research/landscape-containerized-claude.md

@@ -25,7 +25,7 @@ manifest merge.
 ## Other surveyed projects
 
 - **textcortex/claude-code-sandbox → spritz** — evolved toward
-  Kubernetes-native multi-agent infra; not bash-first or local-Docker.
+  Kubernetes-native multi-agent infra; not stdlib-first or local-Docker.
   Original sandbox repo is archived.
 - **trailofbits/claude-code-devcontainer** — devcontainer config for security
   audits; not a general agent launcher.
@@ -58,7 +58,7 @@ None combine:
 Worth publishing. Differentiators that matter to the target audience (power
 users running parallel Claude Code sessions with distinct personas/tooling):
 
-- The bash-first, low-dependency design — competitors are npm-based or
+- The Python-stdlib-first, low-dependency design — competitors are npm-based or
   Kubernetes-native.
 - Named agents with distinct skills and system prompts, not just language profiles.
 - SSH forwarding without key copying.