feat: resolve markdown blank-line formatting inconsistency in post me…

[91-enjoy]

Summary

Simplifies the markdown-to-post rendering pipeline in the IM shortcut. The previous
implementation split markdown at blank-line boundaries into multiple post paragraphs,
using zero-width space (\u200B) sentinel characters to preserve visual spacing.
While well-intentioned, this approach introduced fragility around edge cases such as
blank lines inside fenced code blocks, messages with only blank lines, and interactions
with the heading-normalization pass. This change consolidates rendering back into a
single {"tag":"md"} segment, making the output more predictable, the code significantly
easier to follow, and the test surface easier to maintain.

Changes

• Consolidate wrapMarkdownAsPost and resolveMarkdownAsPost to produce a single-segment
  post payload directly, without dispatching through a multi-step segmentation pipeline
• Inline the code-block protection logic (placeholder substitution and restoration)
  directly into optimizeMarkdownStyle, removing the need for standalone
  protectMarkdownCodeBlocks / restoreMarkdownCodeBlocks helpers
• Remove intermediate abstractions that were only required by the multi-segment path:
  markdownPart struct, shouldUseSegmentedPost, splitMarkdownByBlankLines,
  marshalMarkdownPostContent, buildSingleMDPost, buildSegmentedPost,
  buildMarkdownPostContent
• Remove reBlankLineSeparator regex and the postBlankLinePlaceholder /
  markdownCodeBlockPlaceholder package-level constants
• Clean up test helpers (decodePostContentForTest, decodePostParagraphForTest)
  and all test cases that covered the removed multi-segment behavior; simplify
  the remaining TestWrapMarkdownAsPost to assert on the raw JSON structure

Test Plan

• go test ./shortcuts/im/... -race passes
• go build ./... passes with no errors
• TestOptimizeMarkdownStyle (heading normalization, table formatting, code-block
  protection, excess-newline compression) remains fully covered and unchanged
• Manual local verification confirms the lark im message send --markdown flow
  works as expected

Related Issues

• None

Summary by CodeRabbit

Release Notes

• Bug Fixes

  • Improved markdown content formatting—posts now render as optimized single blocks instead of segmented content blocks.

• Tests

  • Updated test cases to validate refined markdown rendering behavior.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR consolidates markdown-to-Feishu post rendering. Instead of emitting segmented "text" paragraphs split on blank lines, both DryRun and Execute paths now return a single unified "md" block with optimized markdown content. Code-block handling is inlined within optimizeMarkdownStyle. Tests are simplified to validate the new unified format.

Changes

Markdown-to-Feishu Post Rendering Consolidation

Layer / File(s)	Summary
Markdown optimization refactoring shortcuts/im/helpers.go	Regex patterns consolidate into a var block. optimizeMarkdownStyle inlines code-block placeholder extraction and restoration using a local marker constant, eliminating external helper logic.
Post rendering consolidation to single "md" block shortcuts/im/helpers.go	wrapMarkdownAsPost and resolveMarkdownAsPost are simplified to emit a single Feishu post JSON with one "md" paragraph and optimized markdown, removing blank-line segmentation and multi-block generation.
Test alignment and cleanup shortcuts/im/helpers_test.go, shortcuts/im/coverage_additional_test.go	encoding/json import and JSON-decoding helpers removed. Segmented-paragraph test deleted. Assertions updated to validate consolidated "md" block output via substring checks instead of JSON unmarshaling.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• larksuite/cli#338: Both PRs modify markdown post rendering in shortcuts/im/helpers.go; this PR consolidates the segmented "text" blocks introduced in that PR back to a single "md" format.
• larksuite/cli#893: Both PRs refactor wrapMarkdownAsPost/resolveMarkdownAsPost to emit a single "md" block and update test expectations accordingly.
• larksuite/cli#206: Both PRs modify markdown-to-Feishu post rendering; this PR standardizes to single "md" block while the other PR explores alternative link tokenization paths.

Suggested labels

domain/im, size/M

Suggested reviewers

• YangJunzhou-01

Poem

🐰 Segmented posts once split like carrot sticks,
Now unified as one smooth markdown mix—
Code blocks tucked safely, optimization clicks,
A single "md" block, where simplicity sticks!
The tests sing in harmony, no more tricks. ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 28.57% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is truncated (70 chars) but clearly refers to the main change: simplifying markdown blank-line formatting in post messages, which directly aligns with the changeset's core objective.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The PR description provides a comprehensive summary, detailed list of changes, and completed test plan matching the required template structure.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[codecov]

Codecov Report

❌ Patch coverage is 64.28571% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.19%. Comparing base (70081f6) to head (91c17e3).
⚠️ Report is 32 commits behind head on main.

Files with missing lines	Patch %	Lines
shortcuts/im/helpers.go	64.28%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1216      +/-   ##
==========================================
+ Coverage   68.23%   69.19%   +0.96%     
==========================================
  Files         617      633      +16     
  Lines       57176    59492    +2316     
==========================================
+ Hits        39013    41166    +2153     
- Misses      14933    15010      +77     
- Partials     3230     3316      +86     

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[github-actions]

🚀 PR Preview Install Guide

🧰 CLI update

npm i -g https://pkg.pr.new/larksuite/cli/@larksuite/cli@91c17e35239a131f6e84823e8a62e39b716db144

🧩 Skill update

npx skills add 91-enjoy/cli#feat/resolve-markdown-blank-line -y -g