perf(catalog): extend client-tab shell to course and teacher detail pages

[tiankaima]

Summary

#703 shipped client-side tabs for section detail (/catalog/sections/[jwId]?tab=), collapsing 7 tab URLs into one SSR shell. Production still serves full SSR for legacy course and teacher tab paths.

Evidence (v1.81.1, ~12.4h since 2026-07-30T21:48:56Z)

route	anonymous page finishes
/catalog/sections/[jwId]	4,754
/catalog/sections/[jwId]/[section]	8 (redirects working)
/catalog/courses/[jwId]/[section]	329
/catalog/teachers/[id]/[section]	287

Course/teacher tab paths still drive ~616 extra SSR renders in this window — same class of crawler/tab-burst cost #703 addressed for sections.

Scope

Mirror #703 architecture for course and teacher detail:

• single SSR shell + ?tab= client navigation
• 308 redirects from legacy tab paths
• lazy tab panel loading for non-overview tabs
• preserve auth/locale/cache safety boundaries from [perf] Attribute and remove Worker resource-limit and section SSR tail latency #530

Acceptance

• Legacy course/teacher tab paths redirect to shell + ?tab=.
• E2E covers tab navigation and deep links.
• Post-deploy 24h: measurable drop in /catalog/courses/[jwId]/[section] and /catalog/teachers/[id]/[section] SSR count at equal traffic.

Related

• feat(section-detail): client tabs to collapse 7 SSR routes into one shell #703 (section tabs, merged)
• [perf] Attribute and remove Worker resource-limit and section SSR tail latency #530 (attribution / acceptance window)