feat(parser): add Reasonix session support (#733)

## Summary
- Add first-class Reasonix session discovery and parsing so Reasonix activity syncs into agentsview.
- Wire Reasonix through the sync engine's file-based parser switch, the watcher's path classifier, and the registry completeness tests so discovery reaches import on both initial sync and live file changes.

## Scope
- New parser coverage is limited to the Reasonix JSONL transcript + `.jsonl.meta` sidecar described in #720, across all four documented layouts: project sessions, global sessions, global subagents, and archive sessions.
- Project association is preserved from discovery through to the parsed session, and metadata timestamps from `.jsonl.meta` sidecars are kept when present rather than overwritten during parsing.
- No pricing, PostgreSQL-only behavior, or desktop-specific UI changes are part of this slice.

## Review Notes
- `internal/parser/reasonix.go` covers the path layout, transcript-field mapping, and metadata sidecar fallback.
- `internal/sync/engine.go` has two additions: `processReasonix` for the file processor switch, and a Reasonix branch in `classifyOnePath` for watcher-triggered syncs.
- `internal/parser/types_test.go` and `internal/parser/reasonix_test.go` cover registry guardrails, timestamp preservation, and space-containing session IDs.
- Validation ran locally with `CGO_ENABLED=1 go test -tags "fts5,kit_posthog_disabled" ./internal/parser/... ./internal/sync/... -run "Reasonix|Registry" -count=1`; broader CI covers the rest of the Go matrix.

Fixes #720


Co-authored-by: Rod Boev <rodboev@users.noreply.github.com>

Author: rodboev

README.md

@@ -301,6 +301,7 @@ agentsview auto-discovers sessions from all of these:
 | QClaw                 | `~/.qclaw/agents/`                                                                                                                                                      |
 | Qwen Code             | `~/.qwen/projects/`                                                                                                                                                     |
 | QwenPaw               | `~/.copaw/workspaces/`, `~/.qwenpaw/workspaces/`                                                                                                                        |
+| Reasonix              | `~/.reasonix/`, `%APPDATA%\\reasonix\\` (Windows)                                                                                                                       |
 | VSCode Copilot        | `~/Library/Application Support/Code/User/` (macOS)                                                                                                                      |
 | Visual Studio Copilot | `%LOCALAPPDATA%\\Temp\\VSGitHubCopilotLogs\\traces\\` (Windows), `~/Library/Caches/VSGitHubCopilotLogs/traces/` (macOS), `~/.cache/VSGitHubCopilotLogs/traces/` (Linux) |
 | Warp                  | `~/.warp/` (platform-dependent)                                                                                                                                         |