docs: fix typos and improve grammar across documentation

[giwaov]

Fixes various typos and grammatical errors in the Psyche documentation:

• Fixed awkward phrasing in health check description (glossary.md)
• Fixed possessive "it's" → "its" (glossary.md)
• Fixed "neccesary" → "necessary" (join-run.md)
• Fixed "your have" → "you have" (join-run.md)
• Fixed "minumum" → "minimum" (run-config.md)
• Fixed "asssumes" → "assumes" (models.md)
• Fixed duplicate "mostly is mostly" → "is mostly" (index.md)
• Fixed "Here's is" → "Here's" (general-workflow.md)