Feat: Adds slack docs search subcommand

[lukegalbraithrussell]

Changelog

Adds slack docs search subcommand. It can output search results as JSON

Summary

slack docs search

Option	Type	Default	Description	Required
<query>	string		Search terms	Required
--output	string	json	Output format: browser or json	Optional
--limit	int	20	Max number of results to return (JSON output only)	Optional

Examples

# Search and return JSON results
$ slack-cli docs search "Block Kit"

# Search and return JSON results with custom result limit
$ slack-cli docs search "api" --limit=5

# Search and open results in browser
$ slack-cli docs search "webhooks" --output=browser

Code coverage notes

The following lines in search.go have incomplete test coverage. They seemed cumbersome to cover.
(Summarized by Claude)

• Lines 88-89 (if cfg.output == "json" branch): Conditional routing logic that's difficult to test through the command framework. The actual JSON output logic is thoroughly tested via direct function calls.

• Lines 129-130 (JSON encoding error handling): Defensive error handling for an unrealistic scenario (broken pipe when piping output). Most CLI tools don't explicitly handle this edge case.

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

❌ Patch coverage is 93.93939% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.35%. Comparing base (97fbfe8) to head (e1b0d80).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/docs/search.go	93.10%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #433      +/-   ##
==========================================
+ Coverage   70.27%   70.35%   +0.08%     
==========================================
  Files         220      221       +1     
  Lines       18498    18559      +61     
==========================================
+ Hits        12999    13057      +58     
- Misses       4324     4327       +3     
  Partials     1175     1175              

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[lukegalbraithrussell]

This will be updated to docs.slack.dev once api endpoint PR is merged in private docs repo

[srtaalej]

left some comments about terminal ouput and tests but these changes are looking really good ⭐ ! lets get those addressed so we can merge 😝

[srtaalej]

it'd be nice if URLs were full https://docs.slack.dev URLs so they're cmd+clickable in the terminal

{
      "url": "https://docs.slack.dev/block-kit/",
      "title": "Block Kit"
    },

right now the json outputs as

 {
      "url": "/block-kit/",
      "title": "Block Kit"
    },

[srtaalej]

these tests are using full URLs in mocks but the real API returns relative paths — so the tests aren't catching this. a simple fix would be to append to the api output.
something like "https://docs.slack.dev" + result.URL