Stabilize dev app launch verification

[robinebers]

TL;DR

Make the local build-and-run script wait for the previous app process to finish and poll the replacement launch, eliminating a teardown race that could make a successful release verification look like a failure.

What was happening

• The script sent pkill and immediately began rebuilding without confirming that the prior menu-bar process had exited.
• verify slept for a fixed second and checked once, so process teardown or launch timing could produce a false failure.

What this changes

• Waits up to five seconds for the prior process to exit after requesting termination.
• Polls the new process for up to five seconds and reports lifecycle timeouts loudly.
• Documents the bounded lifecycle checks in the debugging guide.

Tests

• bash -n script/build_and_run.sh
• git diff --check
• Three consecutive ./script/build_and_run.sh verify cycles, including one clean release build and two cached rebuilds; every cycle built, signed, launched, and printed ==> running.

---

Note

Low Risk
Changes are limited to the local dev shell script and debugging docs; no runtime app or auth logic is modified.

Overview
build_and_run.sh now blocks on app lifecycle instead of firing pkill and rebuilding immediately. Every run waits up to five seconds for the prior OpenUsage process to exit (fails with a clear error on timeout), and verify polls for up to five seconds after launch instead of a fixed one-second sleep plus a single pgrep.

docs/debugging.md documents those bounded waits and tightens how the dev bundle differs from release: app preferences and single-instance state stay on the dev bundle id, while provider credentials, databases, keychain, and API-key files remain shared on purpose.

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[robinebers]

Superseded by #949, which combines deterministic process lifecycle verification with the warning-free build gate in one cohesive quality-tooling PR. #949 preserves this script/docs fix, is fully green, and is substantially easier to review. This branch remains preserved; nothing was merged.