chore: delete unused gardener/recipes — formulas are the source of truth

These 4 recipe files (cascade-rebase, chicken-egg-ci, flaky-test,
shellcheck-violations) are never referenced by any script.
The gardener uses formulas/run-gardener.toml.

Closes #23

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

gardener/recipes/cascade-rebase.toml

@@ -1,16 +0,0 @@
-# gardener/recipes/cascade-rebase.toml — PR outdated after main moved
-#
-# Trigger: PR mergeable=false (stale branch or dismissed approval)
-# Playbook: rebase only — merge and re-approval happen on subsequent cycles
-#   after CI reruns on the rebased branch (rebase is async via Gitea API)
-
-name        = "cascade-rebase"
-description = "PR outdated after main moved — mergeable=false or stale approval"
-priority    = 20
-
-[trigger]
-pr_mergeable = false
-
-[[playbook]]
-action      = "rebase-pr"
-description = "Rebase PR onto main (async — CI reruns, merge on next cycle)"

gardener/recipes/chicken-egg-ci.toml

@@ -1,25 +0,0 @@
-# gardener/recipes/chicken-egg-ci.toml — PR introduces CI step that fails on pre-existing code
-#
-# Trigger: New .woodpecker/*.yml in PR + lint/check step + failures on unchanged files
-# Playbook: make step non-blocking, create per-file issues, create follow-up to remove bypass
-
-name        = "chicken-egg-ci"
-description = "PR introduces a CI pipeline/linting step that fails on pre-existing code"
-priority    = 10
-
-[trigger]
-pr_files              = '\.woodpecker/.*\.yml$'
-step_name             = '(?i)(lint|shellcheck|check)'
-failures_on_unchanged = true
-
-[[playbook]]
-action      = "make-step-non-blocking"
-description = "Make failing step non-blocking (|| true) in the PR"
-
-[[playbook]]
-action      = "lint-per-file"
-description = "Create per-file fix issues for pre-existing violations (generic linter support)"
-
-[[playbook]]
-action      = "create-followup-remove-bypass"
-description = "Create follow-up issue to remove || true once fixes land"

gardener/recipes/flaky-test.toml

@@ -1,20 +0,0 @@
-# gardener/recipes/flaky-test.toml — CI fails intermittently
-#
-# Trigger: Test step fails + multiple CI attempts (same step, different output)
-# Playbook: retrigger CI (max 2x), quarantine test if still failing
-
-name        = "flaky-test"
-description = "CI fails intermittently — same step fails across multiple attempts"
-priority    = 30
-
-[trigger]
-step_name    = '(?i)test'
-min_attempts = 2
-
-[[playbook]]
-action      = "retrigger-ci"
-description = "Retrigger CI (max 2 retries)"
-
-[[playbook]]
-action      = "quarantine-test"
-description = "If still failing, quarantine test and create fix issue"

gardener/recipes/shellcheck-violations.toml

@@ -1,20 +0,0 @@
-# gardener/recipes/shellcheck-violations.toml — ShellCheck step fails
-#
-# Trigger: Step named *shellcheck* fails with SC#### codes in output
-# Playbook: parse per-file, create one issue per file, label backlog
-
-name        = "shellcheck-violations"
-description = "ShellCheck step fails with SC#### codes in output"
-priority    = 40
-
-[trigger]
-step_name = '(?i)shellcheck'
-output    = 'SC\d{4}'
-
-[[playbook]]
-action      = "shellcheck-per-file"
-description = "Parse output by file, create one fix issue per file with specific SC codes"
-
-[[playbook]]
-action      = "label-backlog"
-description = "Label created issues as backlog"