refactor(controller): declarative reconcile stage pipeline (canary + …

[zachaller]

…blue-green)

Replace the hand-rolled canary and blue-green reconcile chains with a shared stage table and executor while preserving all existing early-return, error-propagation, and status-sync semantics. Behavioral fixes from #4963 (#4626, conditions, cosmetic-stage loosening) are intentionally deferred.

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this is a chore.
• The title of the PR is (a) conventional with a list of types and scopes found here, (b) states what changed, and (c) suffixes the related issues number. E.g. "fix(controller): Updates such and such. Fixes #1234".
• I've signed my commits with DCO
• My builds are green. Try syncing with master if they are not.
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• I have run all tests locally (including the flaky ones) and they pass on my workstation
• I have used LLM/AI/Agent tools for this PR but I am responsible for all code of this PR
• I understand what the code does and WHY/HOW it works in several scenarios
• I know if my code is just adding new functionality or changing old functionality for existing users
• My organization is added to USERS.md.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
5.8% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

Published E2E Test Results

  4 files    4 suites   4h 15m 16s ⏱️
149 tests 135 ✅  7 💤  7 ❌
616 runs  571 ✅ 28 💤 17 ❌

For more details on these failures, see this check.

Results for commit 1a335f0.

[github-actions]

Published Unit Test Results

2 633 tests   2 633 ✅  3m 31s ⏱️
  131 suites      0 💤
    1 files        0 ❌

Results for commit 1a335f0.

[codecov]

Codecov Report

❌ Patch coverage is 72.54902% with 42 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.15%. Comparing base (9f8d111) to head (1a335f0).

Files with missing lines	Patch %	Lines
rollout/stages.go	72.02%	22 Missing and 18 partials ⚠️
rollout/bluegreen.go	60.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4982      +/-   ##
==========================================
+ Coverage   85.12%   85.15%   +0.03%     
==========================================
  Files         166      167       +1     
  Lines       19453    19534      +81     
==========================================
+ Hits        16560    16635      +75     
- Misses       2035     2040       +5     
- Partials      858      859       +1     

Flag	Coverage Δ
e2e	53.18% <72.54%> (+0.20%)	⬆️
unit-tests	81.60% <61.43%> (-0.05%)	⬇️

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