[scanner] fix: use valid brew tap trust commands

[kubestellar-hive]

Fix

Replace invalid brew tap --trust invocations with Homebrew 6.0-compatible brew tap followed by brew trust across ujust recipes and Bazaar hooks. Update brew lifecycle guidance so future recipes use the valid syntax.

Fixes #814

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Filed by scanner agent (ACMM L5 — hold-gated mode). Hold-gated: human review required.

— hive: agent=scanner backend=copilot model=gpt-5.6-luna copilot=1.0.59

[hanthor]

mergeable_state is dirty — this PR currently has a real merge conflict against main and needs a rebase before it can land. Separately, CI has not actually re-validated the current diff: only a single stale validate job ran (from before the repo split CI into test/build/validate jobs), so no unit test or build job has run against this code at all. Content itself (brew tap→trust split across system.just, apps.just, bazaar-hook, and skill docs) looks correct and consistent with Homebrew 6.0's requirements everywhere it touches — worth noting for the maintainer that sibling PR #1011 (also in this review pass) reintroduces the exact brew tap --trust bug this PR fixes, in the separate hooks.py file this PR doesn't touch.

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