Rename SMALLSASS_ACCOUNT_ settings to CAPACITYLENS_

[Kevinjohn]

Part of #1407 (T15). Merge predecessor: #1416 (this PR's base branch).

• Every SMALLSASS_ACCOUNT_X setting is renamed to CAPACITYLENS_X across server, scripts, e2e, workflows, compose, packaging, docs and stories (D1). No aliases: operators rename their variables (CHANGELOG entry).
• Single-product wording replaces the sibling/family framing in DECISIONS.md, the account-boundary note and shared account comments.
• Left as is: CHANGELOG history, the archived SSO cutover design note, removed names quoted in the dated 2026-07-14 security review, and the internal smallsass-account: digest domain tag, which hashes stored ledger values and is not configuration.

Validation: integrated with the rest of Batch 2 and Batch 3 (T7, T15, T6, T8, T16) on 84ae32e7 over origin/main da72918: pnpm run gate:all and pnpm run e2e (290 tests) pass on Node 24.16.0. Independently reviewed before E2E; review findings fixed.

Merge order

1. Route support to Discussions and remove PR screenshots #1411, Add project status, comparison, testing and philosophy pages #1412, Archive changelog sections before 0.41.0-alpha.3 #1414 (independent)
2. Add a first-change path for contributors #1413 (after Archive changelog sections before 0.41.0-alpha.3 #1414), Restate the comment standard as numbered voice rules #1415, Reduce configuration and hide password MFA #1416
3. Rename SMALLSASS_ACCOUNT_ settings to CAPACITYLENS_ #1417 → Add an init command that writes the environment file #1418
4. Retire unused settings and derive engagement grouping #1419 → Move diagnostics to an Owner and Admin page #1420 → Reshape the documentation into four role guides #1421 → Use @/ for app imports that leave their folder #1422 → Consolidate server test scaffolding #1423 → Normalise server route handlers and reply messages #1424 → Apply the comment-voice rules and check them in the gate #1425 (Apply the comment-voice rules and check them in the gate #1425 also after Restate the comment standard as numbered voice rules #1415) → Name the tenant boundary account in code #1426

Merge predecessor for this PR: #1416.

[Kevinjohn]

Polish review: no P1/P2 findings.

• Independent review: no reader of a SMALLSASS_ACCOUNT_ name remains in code, scripts, workflows, compose files, packaging or e2e helpers. The remaining hits are the CHANGELOG history, the archived SSO design note, the dated 2026-07-14 security review and the unchanged smallsass-account: digest domain tag.
• Ladder passes on Node 24: format, lint, typecheck, file sizes, server tsc, crypto inventory, account conformance, the full server suite and the release packaging test.

Merge order for this batch: #1411, #1412, #1414 → #1413, #1415, #1416 → #1417 → #1418, #1419 → #1420 → #1421 → #1422 → #1423 → #1424 → #1425 → #1426. Predecessor: #1416.