fix(skills): UUID resolution, ambiguity errors, delete command, short IDs

[scotthavird]

Summary

Closes the four CLI gaps that surfaced while installing one global skill:

1. Silent name-match selection. `findSkillByName` returned the first match. Renamed to `resolveSkill` — accepts name or UUID, errors loudly on ambiguous names with each candidate's UUID/scope/confidence/state.
2. No way to address a skill by ID. Every command that took `` now also accepts a UUID.
3. No CLI delete. Added `promptconduit skills delete <name|uuid> [--yes]` → `DELETE /v1/skills/:id` (soft). Requires `--yes` on non-TTY.
4. `list` didn't expose IDs. Text output now shows the first 8 chars of each UUID as a prefix column.

Plus: API client gains `GetSkill(id)`, `DeleteSkill(id)`, and a `deleteRequest` helper paralleling `patchRequest`.

Why now

Repeated runs of `skills generate` create duplicate skills with the same name but different IDs (the platform doesn't dedup across detection runs). Before this change, the CLI silently picked the first match — could approve, install, or reject the wrong row without any signal. Caught it manually this week; would have caused real damage in scripted/CI use.

Behavior contract

Scenario	Before	After
`install foo` with 2 `foo` rows	Silently picks first	Errors with both UUIDs + scope + state
`install `	N/A (UUIDs rejected by name validation)	Hits `GET /v1/skills/:id`, installs that exact row
`approve ` with duplicates	Silently picks first	Same disambiguation error as install
`delete `	Didn't exist	Confirms on TTY, requires `--yes` on non-TTY
`list` text output	Just `/name`	`<8-char-id> /name` so you can copy a UUID directly

Test plan

• 10 new tests covering UUID resolution, name resolution (single+ambiguous), empty input, 404 on missing UUID, install-by-UUID disambiguation, ambiguity surfacing IDs in install error, delete via name + UUID, non-TTY refusal without `--yes`
• All existing tests pass (`make test`)
• Lint clean (`make lint` shows no new issues in changed files)
• Smoke against prod: deleted the dupe `git-pr-workflow` row via CLI, approved + installed the survivor, file landed at `~/.claude/skills/git-pr-workflow/SKILL.md`

Out of scope (separate ticket)

• Repo-detection bug where workspace-root sessions all tag as `promptconduit` regardless of which sub-repo edits happened. Different problem (CLI behavior at session start), bigger blast radius, deserves its own design.

Ships as v0.3.6 — additive, no breaking changes.