fix(bitcoin): repair the startup script I broke in 1.7.124, and gate against it

The bitcoin app vanished from updated nodes: the container exited instantly
with 'sh: Syntax error: "fi" unexpected'. My 1.7.124 change added an
explanatory comment INSIDE the manifest's folded YAML scalar (>-), where
'#' is not a comment — it is literal text that reaches the shell. Folding
joins lines with spaces, so the comment swallowed the 'if ... then' while
the more-indented echo survived as its own line, leaving an orphan 'fi'.
bitcoind never ran, the container exited, and the app disappeared from the
UI because detection is container-based.

Explanations now live above the '- >-' line where YAML really treats them
as comments. The loopback-conf tolerance (-allowignoredconf=1) is unchanged
and still needed.

Adds scripts/check-manifest-shell.py to the release gate: it runs 'sh -n'
over every embedded manifest script and rejects '#' inside these scalars.
Nothing validated this shell before — no YAML parse or Rust test could have
caught it, and it only failed on the node, after signing.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/release/run.sh

@@ -62,6 +62,7 @@ summary() {
 # ── Stage 1: static ──────────────────────────────────────────────────
 stage "git-diff-check"   git diff --check
 stage "cargo-fmt"        timeout 240 cargo fmt --manifest-path core/Cargo.toml --all --check
+stage "manifest-shell"  python3 scripts/check-manifest-shell.py
 stage "catalog-drift"    python3 scripts/check-app-catalog-drift.py --release --strict
 # Every release must surface its CHANGELOG entry in the Settings "What's New"
 # modal. The modal hardcodes a block per version and has drifted behind before