docs: add portfolio share package summary

[saagpatel]

What

• Added a compact share-package summary to the portfolio handoff bundle.
• Captured the exact public artifact order for sending or posting the package.
• Added attach-vs-link guidance and ready-to-use captions for portfolio, LinkedIn, recruiter, DM, and video contexts.

Why

The public demo and portfolio assets are now verified and linked, but the final handoff needed a practical "send this" layer so the package can be shared without re-deciding which files to attach, which links to include, or how to describe the sanitized demo.

How

• Added a Share Package section after the current artifact inventory.
• Marked the one-pager PDF, screenshot contact sheet, and deck PDF preview as the recommended attachment set.
• Marked the repo, case study, sanitized demo plan, video script, and rehearsal kit as links, with full public URLs for off-repo sharing.
• Reiterated that the PPTX is a local editable rebuild output, not the committed public preview.

Testing

• pnpm exec prettier --check docs/demo/portfolio-handoff-bundle.md
• Share-package link and required-path existence check.
• Sanitized boundary scans for private/company placeholders and stale device-policy examples.
• Stale text scan for old test counts, old gap labels, stale deck-preview notes, public PPTX links, and hype words in the share section.
• pdfinfo sanity checks for one-pager and deck PDFs.
• sips dimension checks for contact sheet, one-pager PNG, and workspace screenshot.
• node scripts/ci/check-workstation-preflight.mjs
• node scripts/ci/check-workflow-command-drift.mjs
• node scripts/ci/check-version-parity.mjs
• git diff --check
• Git branch, atomic, generated, large-file, and secrets guards.

Risks

Low. Documentation-only change. The main risk is future share-message drift if artifacts are regenerated without updating this handoff.

Performance impact

None expected. Documentation-only change; no runtime, bundle, API, database, or UI behavior changed.

Lockfile rationale

No lockfiles changed.

Screenshots

Not applicable. Documentation-only change; no UI surface changed.