docs: add SUPPORT.md / public triage policy for OSS alpha #155

Problem

WaveHouse ships alpha as an OSS project, but has no public-facing policy for how the project responds to user issues, questions, or feature requests. Issue templates exist (bug_report.md, feature_request.md) but they ask for input without setting any expectation about what happens after submission — response time, triage cadence, supported question channels, etc.

For a 4-person team about to invite public traffic, the realistic risk is the inverse of what most OSS projects worry about: not "we'll be overwhelmed," but "we'll silently miss the first few real issues and lose credibility before we know it." A short SUPPORT.md framed honestly ("best-effort, no SLA, expect 1-2 day turnaround during early alpha") is more useful than no statement at all.

Proposed Solution

Add SUPPORT.md at the repo root covering:

• Where to ask questions (GitHub Discussions? Issues? Discord/Slack if one exists?)
• Triage cadence ("best-effort during alpha; expect 1–2 business days; security disclosures via SECURITY.md are prioritized")
• What's in scope vs out of scope for support during alpha
• How users should report security issues (cross-link to SECURITY.md)

Link from:

• README.md
• CONTRIBUTING.md
• The bug_report.md / feature_request.md issue templates' footers
• Public docs landing page

Acceptance criteria

• SUPPORT.md exists and is linked from at least README + CONTRIBUTING + both issue templates.
• Wording is honest about the alpha-stage commitment level (don't over-promise).
• AGENTS.md notes the SLA so internal expectations match the public statement.