Add ktavi config set command

[mayashavin]

Sub-task of #96

Summary

Add a ktavi config set <key> <value> command to update individual config values in the project or global config file. Use dot-notation keys (e.g. ktavi config set ai.textModel gpt-4o-mini). Validate values against the zod schema before writing.

Command signature

ktavi config set <key> <value> [--global]

• --global — Update global config at ~/.config/ktavi/config.js instead of project config

Examples

ktavi config set ai.textModel gpt-4o-mini
ktavi config set writing.defaultMode strong
ktavi config set storage.provider cloudinary
ktavi config set markdown.preserveFrontmatterOrder false
ktavi config set image.style "watercolor illustration"
ktavi config set storage.local.outputDir ./out/images --global

Valid keys and value constraints

Key	Type	Valid values
ai.provider	enum	openai
ai.textModel	string	any
ai.imageModel	string	any
markdown.coverField	enum	cover, image, heroImage, ogImage, thumbnail
markdown.preserveFrontmatterOrder	boolean	true, false
writing.defaultMode	enum	light, medium, strong
image.size	enum	1024x1024, 1536x1024, 1792x1024
image.style	string	any
storage.provider	enum	local, cloudinary
storage.local.outputDir	string	any
storage.local.publicPathPrefix	string	any
storage.cloudinary.folder	string	any

Implementation steps

1. Export validation from config.ts

Export a validateConfig() function wrapping ktaviConfigSchema.parse() so config set can validate before writing. Keeps the schema encapsulated.

2. Extract serializeConfig to shared utility

Currently lives in configInit.ts. Move to src/utils/configSerializer.ts so both config init and config set can use it.

3. Core logic (configSet.ts)

1. Parse dot-notation key into path segments
2. Coerce string value to correct type (boolean for preserveFrontmatterOrder)
3. Determine target file: --global → ~/.config/ktavi/config.js, else → ktavi.config.ts/.js
4. Load existing config via loadSingleConfigFile (or start with {} if none exists)
5. Set the nested value on the config object
6. Validate the full merged config with validateConfig()
7. Serialize and write back
8. Print confirmation: "Set ai.textModel = gpt-4o-mini in ktavi.config.ts"

Key design decisions

• Value coercion: CLI args are always strings. Coerce "true"/"false" → boolean for preserveFrontmatterOrder. Everything else stays as string (enums are string-based).
• Unknown key handling: Reject keys not in the schema with a clear error listing valid keys.
• Missing config file: If no config file exists, create one with just the set value. Detect .ts vs .js by checking for tsconfig.json.
• Validation timing: Validate the complete merged config (defaults + existing + new value) through the zod schema before writing.
• Empty string clears optional fields: config set ai.imageModel "" removes the field from config.

Error messages

$ ktavi config set writing.defaultMode turbo
Error: Invalid value "turbo" for writing.defaultMode
Valid values: light, medium, strong

$ ktavi config set ai.foo bar
Error: Unknown config key "ai.foo"
Valid keys: ai.provider, ai.textModel, ai.imageModel, writing.defaultMode, ...

$ ktavi config set ai.textModel gpt-4o-mini
✔ Set ai.textModel = "gpt-4o-mini" in ktavi.config.ts

Files to create/modify

File	Change
src/core/config.ts	Export validateConfig() function
src/utils/configSerializer.ts	New — extract serializeConfig from configInit.ts
src/cli/commands/configInit.ts	Import serializeConfig from shared utility
src/cli/commands/configSet.ts	New — set command logic
src/cli/commands/config.ts	Register config set subcommand
tests/cli/configSet.test.ts	New — tests

Test plan

Case	Input	Expected
Set string value	config set ai.textModel gpt-4o-mini	Config file updated, confirmed
Set enum value	config set writing.defaultMode strong	Writes strong, validates
Set boolean value	config set markdown.preserveFrontmatterOrder false	Coerces to boolean, writes
Set nested 3-level key	config set storage.local.outputDir ./out	Deep-sets correctly
Invalid enum value	config set writing.defaultMode turbo	Error with valid options listed
Invalid key	config set ai.foo bar	Error with valid keys listed
No config file exists	config set ai.textModel gpt-4o-mini	Creates new config file
Existing config preserved	Set one field	Other fields unchanged
--global flag	config set ai.textModel gpt-4o-mini --global	Writes to global config
Overwrite existing value	Set field with existing value	Old value replaced
Optional field set	config set image.style "pixel art"	Writes optional field
Optional field clear	config set ai.imageModel ""	Removes field from config