feat: add the DeepSeek platform provider and deepseek-flash

Refs #83

The first vendor-cloud chat row in agent/models.yml. The provider label is the
bare word `deepseek` because pi-catalog/src/hosts.ts keys the direct-DeepSeek
behaviour set (max_tokens field, thinking extraBody, thinking-disable mode) off
that exact name and off api.deepseek.com; the house `<api> (<host>)` pattern
would not match and the row would lose the quirks the endpoint answers to.

The key is command-backed (`!cat ~/.config/secrets/deepseek_api_key`, 600), so
no sk-… value enters the tracked tree, and the row declares the model card's own
pair: contextWindow 1048576 / maxTokens 262144, input [text, image], with the
October 2026 peak rate card in cost. Docs move to the new
omp-docs/core/deepseek-provider.md, indexed and logged in the same commit.

omp-docs/log.md

@@ -22,6 +22,23 @@ not restated here — entry, then pointer. That is what the 2026-10-21 audit pas
 newest twelve entries: the facts stayed, the duplicates went, `git log --follow` keeps the
 long form.
 
+## 2026-10-29
+
+### A vendor-cloud provider must be named the way the harness names it
+
+`deepseek` / `deepseek-flash` joins `agent/models.yml` — Frank's DeepSeek platform
+key in `~/.config/secrets/deepseek_api_key` (600, `!cat`-backed), a 1M/262K row,
+the documented compat block. The label breaks the house `<api> (<host>)` pattern on
+purpose: the catalog's host table (`pi-catalog/src/hosts.ts`) keys the
+direct-DeepSeek behaviour set off the literal name `deepseek` (or an
+`api.deepseek.com` URL), so a prettier label silently loses the quirks that make
+the endpoint answer — the `max_tokens` field, the thinking `extraBody`, and the
+thinking-disable mode this API takes. Law: **a provider label is a lookup key, not
+only a display name**; check the table before inventing one, and prove the row with
+a scratch-HOME call (a poisoned-port control is what separates a real auth success
+from a cached one). Page: [core/deepseek-provider.md](core/deepseek-provider.md).
+
+
 ## 2026-10-27
 
 ### Snapcompact audited against frank-archon; the blind frame price is the real limit