refactor: generate summaries only for content changes

[guqing]

What type of PR is this?

/kind improvement
/area core
/milestone 2.20.x

What this PR does / why we need it:

自动生成摘要仅对内容变更时生效

see #7193 (comment) for more details

避免对资源造成浪费如 AI 摘要生成

Which issue(s) this PR fixes:

Fixes #7193

Does this PR introduce a user-facing change?

自动生成摘要仅对内容发生变更时生效

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

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

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 4 lines in your changes missing coverage. Please review.

Project coverage is 57.17%. Comparing base (eff73dc) to head (f3913d2).
Report is 87 commits behind head on main.

Files with missing lines	Patch %	Lines
...a/run/halo/app/core/reconciler/PostReconciler.java	66.66%	1 Missing and 1 partial ⚠️
...halo/app/core/reconciler/SinglePageReconciler.java	66.66%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #7200      +/-   ##
============================================
+ Coverage     56.99%   57.17%   +0.17%     
- Complexity     3999     4047      +48     
============================================
  Files           714      719       +5     
  Lines         24110    24378     +268     
  Branches       1585     1602      +17     
============================================
+ Hits          13742    13937     +195     
- Misses         9756     9822      +66     
- Partials        612      619       +7     

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[ruibaby]

/lgtm

[f2c-ci-robot]

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