> Mux updated this PR on behalf of Mike.

## Stack Context

This stack splits experimental personal skills into smaller reviewable
PRs. Personal skills are user-owned `SKILL.md` files stored by Coder and
injected into chatd alongside workspace skills.

Stack order:
1. #25362 personal skill resolver
2. #25363 storage, permissions, API, and SDK
3. #25365 API test coverage
4. #25366 chattool and chatd integration
5. #25066 settings UI and docs
6. #25386 personal skills slash menu

## What?

Adds the shared personal skill parser and resolver package, plus
reusable skill-name validation exported from `workspacesdk`.

The parser enforces the full personal skill contract: max raw size,
kebab-case name, max name length, and non-empty body.

## Why?

The rest of the stack needs one source-aware resolver for personal and
workspace skills, including collision handling and qualified aliases.
Keeping personal skill constraints in the parser prevents callers from
accidentally parsing invalid personal skills.

## Validation

- `go test ./coderd/x/skills ./codersdk/workspacesdk`
- pre-commit hooks on this branch

> Mux updated this PR on behalf of Mike.

## Stack Context

This PR is the storage, permissions, API, and SDK layer for experimental
personal skills. #25362 has landed on `main`, so this branch is
restacked directly on `main`.

Stack order:
1. #25363 storage, permissions, API, and SDK
2. #25365 API test coverage
3. #25366 chattool and chatd integration
4. #25066 settings UI and docs
5. #25386 personal skills slash menu

## What?

Adds the `user_skills` database table, generated queries, RBAC resources
and scopes, audit resource handling, experimental user-scoped CRUD
endpoints, SDK types, and generated API/site types.

Follow-up review and restack fixes:
- Enforce a bounded personal skill description in parser and database
constraints.
- Return `403 Forbidden` for unauthorized create and update attempts.
- Return explicit conflict responses when soft-deleted users are
targeted.
- Keep user admins out of personal skills, while site owners can read
and delete but not create or update.
- Document trigger-raised constraint names and keep schema constants
covered by tests.
- Reuse `UserSkillMetadata` in the full `UserSkill` SDK response type.
- Generate user skill IDs in Go instead of relying on a database
default.
- Rebase on latest `main` and renumber the user skills migration to
`000502_user_skills`.

## Why?

Personal skills need durable user-owned storage with owner
authorization, limited site-owner moderation, and a hidden API surface
before chatd can consume them.

## Validation

- `make gen`
- `go test ./coderd/database -run '^TestUserSkillSchemaConstants$'
-count=1`
- `go test ./coderd/database/dbauthz -run
'^TestMethodTestSuite/TestUserSkills$' -count=1`
- `go test ./coderd -run '^TestPatchUserSkill$' -count=1`
- `go test ./codersdk ./coderd/database/db2sdk`
- `make lint`
- pre-commit hook on `97fd58108d`

> Mux updated this PR on behalf of Mike.

## Stack Context

This PR is the API test coverage slice in the experimental personal
skills stack. The storage, schema, permissions, API, and SDK
implementation merged in #25363.

Stack order:
1. #25362 personal skill resolver
2. #25363 storage, permissions, API, and SDK
3. #25365 API test coverage
4. #25366 chattool and chatd integration
5. #25066 settings UI and docs
6. #25386 personal skills slash menu

## What?

Adds API and audit tests for personal skill CRUD, validation failures,
limits, authorization, soft-delete cleanup, and audit content tracking.

This PR is now test-only. It does not include migrations, generated
database code, or API implementation changes.

## Why?

The feature touches storage, permissions, and audit behavior. These
tests make the server behavior reviewable and protected without
re-reviewing the implementation that already merged in #25363.

## Validation

- `go test ./coderd -run '^(TestUserSkill|TestPatchUserSkill)' -count=1`
- `go test ./enterprise/coderd -run
'^TestUserSkillAuditDiffTracksContent$' -count=1`
- pre-commit hook via `gt modify --no-edit`

> Mux updated this PR on behalf of Mike.

## Stack Context

This PR builds on #25365 in the experimental personal skills stack and
completes the chat integration.

Stack order:
1. #25362 personal skill resolver
2. #25363 storage, permissions, API, and SDK
3. #25365 API test coverage
4. #25366 chattool and chatd integration
5. #25066 settings UI and docs
6. #25386 personal skills slash menu

## What?

Updates chattool skill formatting and `read_skill` resolution so tools
can read personal skills from the database, then injects personal skill
metadata into chatd prompts and registers the skill-reading tools when
skills are available.

This branch has also been merged with current `origin/main` to resolve
merge conflicts.

## Why?

The chattool and chatd changes need to land together so the intermediate
stack state stays buildable. This completes personal skill availability
in chats without syncing personal skills into workspace filesystems.

## Validation

- `go test -count=1 ./coderd/x/chatd/chattool -run
'TestFormatResolvedSkillIndex|TestReadSkillTool|TestReadSkillFileTool'`
- `go test -count=1 ./coderd/x/chatd -run
'TestPersonalSkillsInSystemPrompt|TestPersonalAndWorkspaceSkillCollisionInSystemPrompt|TestSkillIndexRefreshReplacesStaleAliases|TestFetchPersonalSkillMetadata|TestLoadPersonalSkillBody'`
- `go test -count=1 ./coderd -run 'Test.*UserSkill'`
- `git diff --cached --check`
- `make lint`
- pre-commit hook