docs: Fix documentation typos and formatting

[ibgreen]

Summary

• correct typos and improve phrasing in the main documentation overview
• clarify roadmap notes and upgrade guidance for probe.gl modules
• fix spelling in developer roadmap notes

Testing

• not run (documentation-only changes)

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Codex Task

[coveralls]

Pull Request Test Coverage Report for Build 20338138808

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 65.439%

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Totals
Change from base Build 20316209338:	0.0%
Covered Lines:	2158
Relevant Lines:	3354

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💛 - Coveralls