fix: parse YAML block scalar skill descriptions (#5046)

## Thinking Path

> - Paperclip is the open source control plane teams use to manage AI
agents for work.
> - Company skills are imported from `SKILL.md` files and rely on YAML
frontmatter to describe what each skill does.
> - Multi-line descriptions commonly use YAML block scalars (`>` and
`|`), but the broken parser path behind #4989 reduced those descriptions
to a literal `>` or `|`.
> - The earliest contributor fix for that bug was PR #5046, so this
branch keeps that PR as the canonical merge target instead of replacing
it.
> - Follow-up work from #5071 and #8258 was then transplanted onto this
earlier branch so the final PR preserves contributor credit while still
shipping the strongest complete fix.
> - The resulting change fixes block-scalar parsing in the shared
frontmatter path, aligns server company-skill imports with that shared
parser, and prevents already-stale stored markers from rendering as junk
in the UI.

## Linked Issues or Issue Description

- Fixes #4989
- Refs #2863
- Refs #788
- Related superseded PRs: #5071, #8258

## What Changed

- Kept the original PR #5046 server-side company-skill fix and
regression coverage as the base branch history.
- Added the missing YAML chomping and indicator hardening explored
further in #5071.
- Moved frontmatter parsing to the shared parser path so
`packages/shared`, `packages/skills-catalog`, and server company-skill
imports stay aligned.
- Added UI summary sanitization and fallback handling so stale stored
`>` / `|` values no longer render as visible junk in company-skill
cards.
- Added regression coverage for shared frontmatter parsing,
skills-catalog parsing, company-skill imports, and stale-summary
fallback behavior.

## Verification

- Passed locally: `pnpm exec vitest run
packages/shared/src/frontmatter.test.ts
packages/skills-catalog/src/frontmatter.test.ts
server/src/__tests__/company-skills.test.ts
ui/src/lib/company-skill-summary.test.ts`
- Passed locally: `pnpm --filter @paperclipai/shared typecheck`
- Passed locally: `pnpm --filter @paperclipai/skills-catalog typecheck`
- Not fully runnable in this worktree: `pnpm --filter
@paperclipai/server typecheck` currently fails in `packages/plugins/sdk`
before reaching server code because local workspace `node_modules` type
deps are missing (`TS2688` for `node` / `react`).
- GitHub Actions / PR checks are rerunning on PR #5046 head
`005290b7557725abf748d00f36dd24ea0d919aba`.

## Risks

- Medium-low risk: the fix now touches shared parser code, server
company-skill imports, and UI fallback display rather than only the
server import path.
- The parser is still intentionally narrower than a full YAML
implementation; this change focuses on block-scalar correctness and the
stale-description rendering path relevant to #4989 / #2863.
- This branch intentionally supersedes narrower overlapping work from
#5071 and duplicate work from #8258 once the survivor PR is green.

> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.

## Model Used

- OpenAI Codex / GPT-5-based coding agent with local shell and
code-editing tools enabled.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [ ] If this change affects the UI, I have included before/after
screenshots
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [ ] All Paperclip CI gates are green
- [ ] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Devin Foley <devin@paperclip.ing>

ui/src/pages/NewAgent.tsx

@@ -8,6 +8,7 @@ import { companySkillsApi } from "../api/companySkills";
 import { issuesApi } from "../api/issues";
 import { projectsApi } from "../api/projects";
 import { queryKeys } from "../lib/queryKeys";
+import { resolveSkillSummaryText } from "../lib/company-skill-summary";
 import { AGENT_ROLES, type AdapterEnvironmentTestResult, type AgentPermissions } from "@paperclipai/shared";
 import { Button } from "@/components/ui/button";
 import { Checkbox } from "@/components/ui/checkbox";
@@ -321,6 +322,7 @@ export function NewAgent() {
                 {availableSkills.map((skill) => {
                   const inputId = `skill-${skill.id}`;
                   const checked = selectedSkillKeys.includes(skill.key);
+                  const summaryText = resolveSkillSummaryText(skill, { fallbackKey: true });
                   return (
                     <div key={skill.id} className="flex items-start gap-3">
                       <Checkbox
@@ -330,9 +332,7 @@ export function NewAgent() {
                       />
                       <label htmlFor={inputId} className="grid gap-1 leading-none">
                         <span className="text-sm font-medium">{skill.name}</span>
-                        <span className="text-xs text-muted-foreground">
-                          {skill.description ?? skill.key}
-                        </span>
+                        {summaryText ? <span className="text-xs text-muted-foreground">{summaryText}</span> : null}
                       </label>
                     </div>
                   );