Fix release pipeline: bakery.toml discovery and ECOSYSTEM_DIR on hestia

- Add bakery.toml describing the bakery binary as an installable product
- gen-index.sh: check DL_DIR/<pkg>/bakery.toml first (written by each
  product's release workflow), fall back to sibling checkout for local dev
- gen-index.sh: include bakery itself in the products list
- release.yml: use GITHUB_WORKSPACE instead of ECOSYSTEM_DIR (the
  bread-ecosystem runner IS the checkout, no separate clone needed)
- release.yml: copy bakery.toml to DL_DIR during artifact prep

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

bakery.toml

@@ -0,0 +1,8 @@
+name = "bakery"
+description = "Bread ecosystem package manager"
+binaries = ["bakery"]
+system_deps = []
+bread_deps = []
+
+[install]
+post_install = []