Fletch v0.7.8

What's Changed

• docs: correct sandbox description in README by @alchaplinsky in #396
• fix: move OAuth tokens to the macOS Keychain and wall off the app data dir from agents by @alchaplinsky in #397
• fix: never hold the global agents lock across blocking child I/O by @alchaplinsky in #400
• fix: scrub Sentry payloads before egress (privacy) by @alchaplinsky in #399
• fix(sandbox): narrow agent write grants via shared engine-independent policy by @alchaplinsky in #398
• fix(sandbox): claude config-dir RO-with-islands for seatbelt by @alchaplinsky in #401
• feat: persist follow-up message queue across restarts by @alchaplinsky in #404
• ci: gate on rustfmt and clippy -D warnings by @alchaplinsky in #402
• feat: detect transcript layout drift and surface sync health by @alchaplinsky in #403
• feat(agents): skills library and MCP tool servers for custom agents by @alchaplinsky in #405
• chore: bump version to v0.7.8 by @alchaplinsky in #407

Full Changelog: v0.7.7...v0.7.8