chore(e2e): remove simulation layer and legacy hotfix scenarios

[joshua-temple]

Summary

• Removes the e2e simulation layer (Harness.RunWorkflow/RunWorkflowWithSetup, simulatePromote, simulateHotfix, detectErrorConditions, determineNextVersion/determineHotfixVersion, Harness.Assert) and the TestScenarios entry point, so every scenario now runs as a real multi-step test under act + gitea.
• Makes DiscoverScenarios skip files containing steps: or repos:, so a lifecycle scenario is never also parsed as a degenerate single-step run. This halves container load.
• Deletes the legacy hotfix scenarios (they contradicted the shipped design) and the redundant single-step orchestrate/promote/release scenarios already covered by 01-04/09.
• Rewrites the error scenarios (build failure, missing workflow file) and promote-fails-missing-source as real multi-step tests that assert workflow conclusion failure.
• Adds an environment_config passthrough to the harness Config and fixes the env-gates assertion to newline-anchor on the job-level (4-space) environment: key so it no longer matches the 6-space reusable-workflow with: input.
• Removes the dead changelog: blocks from scenarios 01/02/03 (never consumed by the assertion layer).
• Renumbers duplicate scenario prefixes (09->12 inline-run-callback, 11->13 dispatch-inputs).
• Drops an unused compareState helper to keep the e2e module lint clean.

Verification

• go build ./... and go vet ./... clean on both the root and e2e modules.
• golangci-lint run ./... clean in the e2e module (0 issues).
• Targeted TestMultiStepScenarios runs pass: single/two env (3), three/four env (3), env-gates + build-failure + missing-workflow + promote-fail (5), and harness unit tests (8).
• No hotfix_branch references remain; no duplicate scenario-number prefixes.