docs(prd): fold 0006 walkthrough resolutions into the design

After the open-question walkthrough, all four collapsed:

- Q1 (mount semantics): resolved to `docker cp` between
  `docker create` and `docker start`, mirroring the existing
  pipelock YAML handling. No bind mount, no UID/permission
  concern. Folded into §Proposed Design > CA lifecycle as
  "Sidecar install".
- Q2 (cert validity / TTL): pre-decided in the question text.
  Per-bottle ephemerality is enforced by regenerating per launch,
  not by short validity windows. Pipelock's defaults are fine.
  Folded into §Proposed Design as a one-line "Per-bottle
  ephemerality" note.
- Q3 (`passthrough_domains` shape): not v1 scope; the shape is
  pre-recorded so the follow-up is mechanical. Moved into
  §Out of scope.
- Q4 (stage-dir cleanup ordering): reading start.py confirmed
  the ExitStack-then-outer-finally order is correct. Folded into
  §Proposed Design as a "Teardown" note.

The §Open questions section is dropped. None of the four was a
real design question — they were verifications and pre-decided
items left in for defensiveness.

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

docs/prds/0006-pipelock-tls-interception.md

@@ -136,9 +136,13 @@ The feature is **done** when all of the following ship:
     leaving `ca.pem` and `ca-key.pem` under `stage_dir`. The host
     file owner is whatever the upstream image's user is; the
     sidecar mount is read-only so this is fine.
-  - `DockerPipelockProxy.start` mounts the stage dir into the
-    sidecar at `/h:ro` and references the CA paths in the rendered
-    YAML.
+  - `DockerPipelockProxy.start` `docker cp`s the CA cert + key
+    into the sidecar at `/etc/pipelock/ca.pem` and
+    `/etc/pipelock/ca-key.pem` between `docker create` and
+    `docker start`, mirroring the existing pattern for the YAML
+    config. If pipelock's image runs as non-root, a `docker exec
+    -u 0 chown pipelock:pipelock /etc/pipelock/ca*.pem` lands
+    between the `cp` and the `start`.
 - **`claude_bottle/backend/__init__.py`**: new abstract method
   `provision_ca(plan, target)` on `BottleBackend`, default no-op.
   `BottleBackend.provision` orchestrates `ca → prompt → skills →
@@ -183,7 +187,10 @@ The feature is **done** when all of the following ship:
 - A manifest field to disable / customize interception per bottle.
   Doable but premature.
 - Wiring `passthrough_domains`. The default `[]` is correct for
-  v1; add the manifest field when a pinning host shows up.
+  v1; add the manifest field when a pinning host shows up. The
+  shape is pre-recorded so the follow-up is mechanical:
+  `bottle.egress.tls_passthrough_domains: [host, ...]`,
+  mirroring the existing `egress.allowlist`.
 - `cross_request_detection`, `entropy_budget`,
   `fragment_reassembly`, `reverse_proxy`, `scan_api` — features
   pipelock exposes but we don't need for the body-DLP gap.
@@ -204,21 +211,29 @@ generated at prepare time.
 ### CA lifecycle
 
 - **Generation.** Host-side, at prepare time, via a one-shot
-  `docker run --rm -v <stage>:/h pipelock tls init`. Output is
-  `<stage>/ca.pem` + `<stage>/ca-key.pem`, both mode 600.
-- **Sidecar mount.** `DockerPipelockProxy.start` adds
-  `-v <stage>:/h:ro` to the sidecar's `docker run`. The rendered
-  YAML references `/h/ca.pem` and `/h/ca-key.pem`. The private
-  key is read-only from pipelock's perspective; the host stage
-  dir is owned by the launching user.
+  `docker run --rm -v <stage>:/h -e PIPELOCK_HOME=/h pipelock tls
+  init`. Output: `<stage>/ca.pem` + `<stage>/ca-key.pem`, mode 600.
+- **Sidecar install.** `DockerPipelockProxy.start` `docker cp`s
+  the CA cert + key into the sidecar at `/etc/pipelock/ca.pem`
+  and `/etc/pipelock/ca-key.pem` between `docker create` and
+  `docker start`. Same pattern the proxy already uses for the
+  YAML config — no bind-mount, no UID/permission concern from
+  the one-shot generation step. The rendered YAML references
+  the in-container paths.
 - **Bottle install.** `provision_ca` (Docker impl) does
   `docker cp <stage>/ca.pem agent:/usr/local/share/ca-certificates/claude-bottle-mitm.crt`,
   then `update-ca-certificates`. The CA env trio is set at
   `docker run -e` time (Docker propagates run-time env into
-  `docker exec`, verified in PR #8's spike).
-- **Teardown.** The sidecar container is destroyed, the stage
-  dir is removed by `start.py`'s existing `finally` block, and
-  the CA dies with both.
+  `docker exec`).
+- **Per-bottle ephemerality.** Enforced by *regenerating per
+  launch*, not by validity windows. Pipelock's defaults
+  (`cert_ttl: 24h` for leaves, `--validity 87600h` for the CA)
+  are fine — the CA lives only as long as the sidecar, which is
+  the bottle's lifetime.
+- **Teardown.** Sidecar removed via `ExitStack` callback, then
+  the launch context manager's outer `finally` `shutil.rmtree`s
+  `stage_dir`. CA dies with both, in that order, so the sidecar
+  is never reading a deleted mount on shutdown.
 - **Fingerprint.** Computed via stdlib in `provision_ca` and
   logged once to stderr (`claude-bottle: mitm ca fingerprint:
   sha256:<hex>…`). The private key never appears in any log.
@@ -259,33 +274,6 @@ backend module.
   image's own `tls init` command in a one-shot container.
   Fingerprint uses Python stdlib `ssl` + `hashlib`.
 
-## Open questions
-
-- **Mount semantics for the stage dir.** The sidecar runs with a
-  `-v <host-stage>:/h:ro` bind mount. The CA files were written by
-  the one-shot `pipelock tls init` container with whatever UID
-  pipelock's image uses; the sidecar reads them as that same UID.
-  Should work, but confirm on first impl by inspecting the file
-  modes/owners and that the sidecar actually loads them. Fallback:
-  `docker cp` the cert/key into the running sidecar after `docker
-  create` (mirror PR #8's mitmproxy lifecycle).
-- **Cert validity / TTL.** Defaults are `cert_ttl: 24h` for
-  per-host leaves; the CA validity from `pipelock tls init` is
-  10 years by default (`--validity 87600h`). The CA outlives the
-  bottle either way; per-bottle ephemerality is enforced by
-  *generating a fresh one each launch*, not by setting a short
-  CA validity. Document; no tuning in v1.
-- **`passthrough_domains` shape.** Once we expose this through
-  the manifest in a follow-up, the natural place is
-  `bottle.egress.tls_passthrough_domains: [host, ...]`, mirroring
-  the existing `egress.allowlist` shape.
-- **Stage-dir cleanup ordering.** The stage dir holds the CA
-  private key briefly. `start.py`'s existing `finally` block
-  `shutil.rmtree`s it. Confirm the rmtree fires after the sidecar
-  is stopped, so the sidecar isn't reading a deleted mount when
-  it shuts down. The current order is correct (teardown unwinds
-  via ExitStack before the outer `finally` runs); verify.
-
 ## References
 
 - `docs/research/pipelock-assessment.md` (now corrected) —