fix: check senior-dev capacity across selected services

[ZeroPoint95]

• Fixed senior-dev shell runs to warm the catalogs of the selected services, including custom services, before resolving model capacity.
• Fixed missing or zero capacity in high, low, and frontier pools to stop before pipeline stages or model calls, with guidance to use a known model or provider-supplied limits in senior-dev.json.
• Preserved explicit project limits, offline fallback sizing, tiny-window guards, and credential boundaries.
• Added real shell host/child regressions for listed, configured, missing, and tiny custom-model capacities, plus all-pool and zero-capacity checks.
• Updated the manual with supported custom-model configuration and preserved existing search answers.

Validation:

• Focused custom-service shell, sizing, and preflight tests passed.
• Related senior-dev, delegate, and config suites passed.
• make pr-ready passed against dev 56c1a8b; its classifier reproduced the existing macOS installer-path test failure on that base and reported it as pre-existing.
• Independent review approved the final candidate.
• Real senior-dev acceptance passed with provider-supported context capacity; missing capacity refused before calls or file changes.
• The broader hosted-drive acceptance rerun remains red (9 PASS / 6 FAIL); the first run exceeded its five-minute bound. Staging remains on hold while that separate workflow issue is investigated.