[strategist] Architectures import runs but has no freshness indicator on the page

## Strategic Finding

**Type**: roadmap-gap (Phase 1 pillar: architectures)
**Horizon**: mid-term

`import-architectures.yml` keeps the architectures section in sync with cncf/architecture — the pipeline exists. ROADMAP.md Phase 1's remaining ask for this pillar is a **freshness indicator on the page**: visitors cannot tell whether an architecture entry is current, and a silently-failing import (cf. the recent librsvg2-bin gap, PR #49) would leave stale content up indefinitely.

## Rationale

Reference architectures are the site's most-differentiated content — no other CNCF property surfaces them as a browsable collection. The "Verified facts" principle means every page generated from an upstream source should show its provenance and age. This is the smallest of the six Phase 1 pillars: the data pipeline is done, only the display affordance is missing.

## Proposed Next Step

Surface the import revision/date (already recorded in metrics.json's `sources.architectures`) on the architectures index page as a "last synced from cncf/architecture @ \" line. Acceptance: architectures page shows upstream revision and sync date.

Tracks ROADMAP.md Phase 1 / issue #59.

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*Filed by strategist agent (ACMM L6 — full mode)*