fix(import): preserve missing fragment diagnostics

[0dust]

Summary

Missing Obsidian heading and block warnings now survive conversion into portable Markdown. okfy validate, Inspector, and MCP therefore report the same missing_wikilink_fragment warnings as the original import instead of silently losing them.

Generated bundles persist only the warning provenance that Markdown cannot reconstruct. Each warning is bound to the exact emitted Markdown link and its import-time multiplicity, so an unrelated link cannot keep a removed conversion warning alive. Validation conservatively suppresses stale or ambiguous provenance and still clears warnings after real target repairs.

Plain and JSON CLI presentation now encode C0, DEL, and C1 terminal controls without changing the underlying diagnostic values. This blocks ANSI, OSC, BEL, and C1 injection from untrusted provenance while preserving valid writer-produced paths and JSON round trips.

Malformed or unsafe metadata remains non-fatal and produces one actionable validation warning.

Validation

• pnpm test — 255 tests passed from a clean detached checkout
• Focused validation, Inspector, and MCP regressions — 52 passed
• pnpm typecheck
• pnpm lint
• pnpm build
• Public-surface tests — 11 passed, including a clean npm install
• npm pack --ignore-scripts --dry-run --json
• Independent correctness, testing, API-contract, security, reliability, and simplicity reviews found no actionable issues

Related

• Fixes bug: missing-fragment diagnostics disappear after import #24
• Related: validation: dogfood OKFy with a real-world Obsidian vault #23