feat(presets): bundled preset roles — 7 omp-style generic subagent roles (presets switch, apply self-declare, 0.1.6 minor)

[btspoony]

Summary

Adds bundled preset roles to dsh-llm-fallbacks: 7 omp-style generic subagent roles (designer / librarian / reviewer / scout / security-reviewer / sonic / task) ship with the plugin and are auto-declared on apply via the existing role-seeds surface (FallbacksSeedManager), so dsh hosts get an out-of-the-box generic role taxonomy. Operators can switch them off (presets: 'none'); library consumers can reuse the same data (declareSeeds(presetRoles)).

What changed

• src/presets.ts (new): presetRoles: readonly SeedDeclaration[] — 7 roles, personas distilled from omp bundled-agent prompts (derivation annotated, snapshot 2026-08-16), frozen verbatim in spec §9.2.
• presets config key (default 'bundled', four-way sync): FallbacksConfig 9th optional field + defaultFallbacksConfig + schemastery schema (union-of-const, mirrors revertPolicy) + gateway CONFIG_KEYS.
• src/index.ts: apply-time self-declaration — new tail ctx.inject(['settings']) child fires seeds.declare(presetRoles, seedsIo) with a terminal catch (spec §9.3 D9.3-a/b/c/d: sync apply, no base-only overwrite, multi-fiber ownership gate, presets:'none' live short-circuit, headless zero-side-effect); package-root re-export presetRoles (9-key service unchanged).
• Client chain: parseFallbacksConfig folds the new default (client fold == host defaults invariant), FallbacksCard assembleConfig carries the key (clean/dirty invariant), export-surface.spec.ts SSOT synced.
• Docs (configuration.md, README en/zh-CN, consumer-api.md) + changelog fragment preset-roles.md (category: Added).

Verification

• QC tri: 3× Approve (0 Critical / 0 Warning) — fix wave 46afb90 cleared F-001 flaky window + 4 suggestions; targeted re-review Approve.
• QA gate (mandatory): PASS-WITH-NOTES — AC-1..AC-6 all PASS; pnpm test 558/558 (baseline 539, +19, zero regression); pnpm typecheck clean; pnpm build incl. verify-dist host+client OK; 0 open residuals.
• Boundary (recorded): card badge/revert visual (no standalone harness), real file-backed HMR (MemorySettings simulated).

Release

Targets main; next release minor 0.1.6 (0.1.5 published 2026-08-15) via the existing release pipeline (fragment archived by release-prep).