Entity Pulse step 1 — official-blog-pack standalone + iso-helper for date normalization across packs

First implementation step of the Entity-Pulse-Bundle spec lands as a working two-stage pack (find-index → extract) plus a generic ISO-8601 normalizer that solves date extraction across heterogeneous web sources. Smoke-tested against reach.edu: 5 real blog posts pulled end-to-end with ISO publish dates + computed age_days in 4.4s. SerpApi + Firecrawl wired as new connectors; new NATS subject `pack.entity_pulse.requested`; standalone CLI driver for one-off fires and future Agent Chat integration.