feat: detect VS Code location settings in readiness checks

[digitarald]

Summary

Adds detection of VS Code chat.*Locations settings (instructionsFilesLocations, agentFilesLocations, agentSkillsLocations) from .vscode/settings.json and *.code-workspace files in readiness checks.

Changes

• VS Code location settings: Parse and validate custom file locations from VS Code workspace settings, extending custom-instructions, custom-agents, and copilot-skills readiness criteria
• JSONC trailing comma support: Extended stripJsonComments to handle trailing commas (common in VS Code settings files)
• Bug fix: File-based instructions without detected areas now correctly report as pass
• Readiness convergence: Deleted monolithic readiness.ts (1381 lines), activating the equivalent modular readiness/ directory
• 14 new tests: 11 for VS Code location settings, 3 for JSONC trailing comma handling

Security

• Path traversal (..) and absolute paths rejected via validateAndNormalize
• Repo root (.) rejected to prevent false-positive detection
• All paths from untrusted settings files validated before filesystem access

[Copilot]

Pull request overview

Adds support for discovering Copilot/agent instruction, agent, and skill locations from VS Code workspace settings as part of readiness checks, and improves JSONC parsing to match VS Code’s common file formats (comments + trailing commas).

Changes:

• Parse chat.*Locations from .vscode/settings.json and root *.code-workspace files and thread the results into readiness checks.
• Extend JSONC parsing (stripJsonComments) to also remove trailing commas.
• Refactor readiness implementation by removing the legacy monolithic readiness.ts in favor of the modular services/readiness/ implementation; add tests for the new behavior.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/services/tests/readiness.test.ts	Adds readiness tests covering VS Code location settings for instructions/agents/skills discovery.
src/services/tests/fs.test.ts	Adds unit tests validating trailing-comma stripping behavior in JSONC parsing.
packages/core/src/utils/fs.ts	Extends stripJsonComments to strip trailing commas in addition to comments (JSONC compatibility).
packages/core/src/services/readiness/types.ts	Adds VscodeLocationSettings and threads it through ReadinessContext.
packages/core/src/services/readiness/index.ts	Populates vscodeLocations in readiness context via parseVscodeLocations.
packages/core/src/services/readiness/criteria.ts	Uses VS Code-derived locations for custom-instructions, custom-agents, and copilot-skills.
packages/core/src/services/readiness/checkers.ts	Implements VS Code settings parsing + validation and extends checkers to accept extra directories.
packages/core/src/services/readiness.ts	Deletes the legacy monolithic readiness implementation.

[Copilot]

validateAndNormalize() can incorrectly accept Windows-style absolute paths when running on POSIX. Example: a setting path like \\etc\\agents is not considered absolute by path.isAbsolute() on POSIX, but the later replace(/\\/g, "/") turns it into /etc/agents (absolute). That would make subsequent path.join(repoPath, dir) ignore repoPath and allow filesystem access outside the repo. Consider normalizing separators before the absolute-path check and/or rejecting any normalized path that starts with / or \\, and add a test case for leading-backslash inputs.

Suggested change

	if (!trimmed || path.isAbsolute(trimmed)) return undefined;
	const segments = trimmed.split(/[/\\]+/u);
	if (segments.some((s) => s === "..")) return undefined;
	let normalized = path.normalize(trimmed).replace(/\\/gu, "/");
	normalized = normalized.replace(/\/+$/u, "");
	if (!normalized || normalized === ".") return undefined;
	if (!trimmed) return undefined;
	// Normalize separators first so absolute-path detection is reliable across platforms.
	const sepNormalized = trimmed.replace(/\\/gu, "/");
	// Reject absolute or root-based paths (POSIX, Windows drive letters, UNC, etc.).
	if (path.isAbsolute(sepNormalized) || sepNormalized.startsWith("/")) return undefined;
	const segments = sepNormalized.split(/\/+/u);
	if (segments.some((s) => s === "..")) return undefined;
	let normalized = path.normalize(sepNormalized).replace(/\\/gu, "/");
	normalized = normalized.replace(/\/+$/u, "");
	if (!normalized || normalized === "." || normalized.startsWith("/")) return undefined;

[Copilot]

In custom-instructions, fileBasedInstructions now includes .instructions.md files from VS Code chat.instructionsFilesLocations, but the surrounding comment and success reason still describe these as "area instruction(s)". This can be misleading when the extra locations are not area-specific. Consider updating the wording (and possibly the variable name) to reflect "file-based instructions" rather than "area instructions" when non-.github/instructions/ locations are included.