feat(store): add Research agent with 8 skills and 2 routines

[mukktinaadh]

What this scratches for you

I use Houston daily. Research was the only major business function missing from the store — I kept doing competitive intel and meeting prep manually.

Linked issue

No existing issue — this is a net-new agent filling a clear gap.

Summary

• Adds a research agent to the Houston Store (agent feat: workspace templates, platform positioning, learn guide #9)
• 8 skills: profile-a-competitor, compare-competitors, build-a-dossier, track-a-trend, research-a-market, find-similar-companies, run-due-diligence, monitor-competitor
• 2 routines: weekly competitor pulse (silent-by-default) + monthly market digest
• Follows Houston's exact language rules, don't-say/say pattern, and file conventions

Checklist

• I read the diff myself before opening this PR
• I have no other open PRs on this repo
• pnpm typecheck passes (no TS touched)
• cargo check --workspace passes (no Rust touched)
• cargo test --workspace passes (no Rust touched)
• No external frameworks/methodology imported into knowledge-base/ or docs/