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- Related superseded PRs: #5071, #8258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/storybook/stories/skills-store-discovery.stories.tsx

@@ -14,6 +14,7 @@ const MOCK_CARDS: DiscoveryCard[] = [
     slug: "paperclip-dev",
     author: "Paperclip",
     version: "v2.4.1",
+    tagline: "Run and repair local Paperclip workspaces.",
     description: "Develop and operate a local Paperclip instance.",
     categories: ["devops", "coding"],
     iconUrl: null,
@@ -35,6 +36,7 @@ const MOCK_CARDS: DiscoveryCard[] = [
     slug: "agent-browser",
     author: "here.now",
     version: "v0.8.2",
+    tagline: "Drive browsers from an agent loop.",
     description: "Browser automation CLI for AI agents.",
     categories: ["research", "browsers"],
     iconUrl: null,
@@ -56,6 +58,7 @@ const MOCK_CARDS: DiscoveryCard[] = [
     slug: "verify",
     author: "Paperclip",
     version: "v1.0.3",
+    tagline: "Prove the change works in a real app run.",
     description: "Verify a code change works by running the app.",
     categories: ["testing"],
     iconUrl: null,
@@ -77,6 +80,7 @@ const MOCK_CARDS: DiscoveryCard[] = [
     slug: "hue-prosumer",
     author: "you",
     version: "v0.1.0",
+    tagline: "Remix a design-language skill for production use.",
     description: "Generate design language skills, prosumer remix.",
     categories: ["design"],
     iconUrl: null,
@@ -98,6 +102,7 @@ const MOCK_CARDS: DiscoveryCard[] = [
     slug: "claude-api",
     author: "Anthropic",
     version: "v1.6.0",
+    tagline: "Ship and tune apps on the Claude API.",
     description: "Build, debug and optimize Claude API apps.",
     categories: ["coding", "ai"],
     iconUrl: null,
@@ -119,6 +124,7 @@ const MOCK_CARDS: DiscoveryCard[] = [
     slug: "security-review",
     author: "Paperclip",
     version: "v1.1.0",
+    tagline: "Review a branch for concrete security risks.",
     description: "Security review of pending changes on a branch.",
     categories: ["security"],
     iconUrl: null,
@@ -140,6 +146,7 @@ const MOCK_CARDS: DiscoveryCard[] = [
     slug: "commit-perfect",
     author: "Yuki",
     version: "v3.0.1",
+    tagline: "Tighten commits and PR metadata before review.",
     description: "Polish commits and PR titles before review.",
     categories: ["git", "workflow"],
     iconUrl: null,
@@ -161,6 +168,7 @@ const MOCK_CARDS: DiscoveryCard[] = [
     slug: "deep-research",
     author: "Astra",
     version: "v2.0.0",
+    tagline: "Synthesize multiple sources with citations.",
     description: "Multi-source research with citation-grade synthesis.",
     categories: ["research"],
     iconUrl: null,
@@ -182,6 +190,7 @@ const MOCK_CARDS: DiscoveryCard[] = [
     slug: "paperclip",
     author: "Paperclip",
     version: "core",
+    tagline: "Coordinate company work through the control plane.",
     description: "Control plane API for tasks, routines, and coordination.",
     categories: ["core"],
     iconUrl: null,
@@ -203,6 +212,7 @@ const MOCK_CARDS: DiscoveryCard[] = [
     slug: "diagnose-why-work-stopped",
     author: "Paperclip",
     version: "core",
+    tagline: "Find the exact stop-point in stalled work.",
     description: "Forensics for stalled or looping work trees.",
     categories: ["workflow"],
     iconUrl: null,