opencode prices and Go limits, settings out of .env

- Fetch prices for opencode (Zen and Go) incl. limits, image input, reasoning,
  long-context tiers and peak-hour/date factors; costs apply them per request
- Record the cost opencode reports per response; track Go allowance in 5h/7d/month
  windows against a provider plan limit (budget table, status overlay)
- Settings → Config file: move values of ${NAME} references into the config
- Examples, presets and forms keep keys in the config instead of .env

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -3,6 +3,26 @@
 All notable changes to CodeCraft. Versions follow [Semantic Versioning](https://semver.org/);
 until 1.0, minor versions may contain breaking changes.
 
+## [Unreleased]
+
+### Added
+
+- **opencode prices:** *Fetch prices* reads prices, context and output limits, image input and
+  reasoning from opencode's model list (Zen and Go), including long-context tiers and
+  peak-hour or date-based factors. Costs apply them per request (`price_tiers`,
+  `price_multipliers` on a model).
+- **opencode costs and Go limits:** the cost opencode reports per response is recorded instead
+  of an estimate, and with a *plan limit* on the provider the Go allowance is tracked in the
+  5-hour, 7-day and monthly windows (budget table and status overlay; usage through CodeCraft
+  only).
+- **Settings → Config file** lists `${NAME}` references and moves the values of set variables
+  into the configuration, so `.env` only needs deployment settings.
+
+### Changed
+
+- Examples and forms no longer suggest environment variables for keys; `.env.example` holds
+  deployment settings only.
+
 ## [v202611-00001] – 2026-11-09
 
 ### Added