docs: fix broken links and link consistency across dream-server/docs

[fullstackdev0110]

Summary
Improves link consistency and clarity in dream-server/docs/ so all internal doc links use the same style and readers can tell which FAQ is which.

Changes

• Link style: Use bare filenames for docs in the same directory (e.g. INTEL-ARC-GUIDE.md) instead of docs/ or ../docs/ in SUPPORT-MATRIX, INTEL-ARC-GUIDE, COMPOSABILITY-EXECUTION-BOARD, OSS-LAUNCH-CHECKLIST, EXTENSIONS, and BACKEND-CONTRACT.
• docs/README.md: Add a short “link convention” note (use ../ for repo root, bare names for same-directory docs) and clarify that ../FAQ.md is the installation/usage FAQ at repo root and FAQ.md in this directory is the hardware/requirements FAQ.

Scope

• Touched: 7 files under dream-server/docs/.
• Theme: Doc links and link consistency only; no content or code changes.
• Verification: All link targets were checked; no broken links, only normalization and clarification.

[Lightheartdevs]

Review: docs link consistency fixes

Link correctness: LGTM

All link target files verified to exist under dream-server/docs/:

• INSTALLER-ARCHITECTURE.md, PROFILES.md, TROUBLESHOOTING.md, INTEGRATION-GUIDE.md, SUPPORT-MATRIX.md, HARDWARE-GUIDE.md, INTEL-ARC-GUIDE.md, CAPABILITY-PROFILE.md, PREFLIGHT-ENGINE.md, BACKEND-CONTRACT.md, DREAM-DOCTOR.md, PLATFORM-TRUTH-TABLE.md

The remaining ../ relative links (e.g., ../docker-compose.arc.yml, ../extensions/services/dashboard-api/main.py, ../README.md, ../FAQ.md) also resolve correctly from the dream-server/docs/ directory.

The changes are purely cosmetic — normalizing display text (removing redundant docs/ prefixes) and normalizing hrefs from ../docs/X.md to bare X.md for same-directory links. Both forms already worked, but bare filenames are the correct canonical form for same-directory references, so this is a good cleanup.

docs/README.md convention note

The added link-convention blurb in docs/README.md is a useful addition that documents the pattern for future contributors.

Conflict with PR #223

Important: PR #223 (chore/clean-dream-server-dev-files) moves the entire dream-server/docs/ directory to docs/ at the monorepo root. Since PR #366 touches 7 files under dream-server/docs/, merging #223 first will cause merge conflicts on every file in this PR — the paths won't exist anymore.

However, the content of #366 (bare-filename same-directory links) remains correct after the move since the docs files stay in the same directory relative to each other. So the merge order doesn't matter for correctness, only for conflict resolution:

• If #366 merges first: #223 will auto-resolve the renames (git handles rename + content change well).
• If #223 merges first: #366 will need to be rebased to target docs/ instead of dream-server/docs/.

Recommendation: Merge #366 before #223 for the cleanest path, or rebase #366 after #223 if that ships first.

Verdict

No broken links, no missing targets, correct normalization. Clean PR. Ship it.