#1233 Docs: update manual telemetry reference for user-global spool and telemetry.yaml opt-out

Follow-up to #1129 and #1125.

Telemetry is now user-global (not repo-local). The following manual pages in content/manual/reference/ need updating:

repository-configuration.md

• The telemetryDisabled field documents per-repo opt-out but doesn't mention the user-global ~/.config/swamp/telemetry.yaml disabled: true opt-out for repo-less runs.
• The priority order should include all four layers: --no-telemetry flag → SWAMP_NO_TELEMETRY env var → .swamp.yaml telemetryDisabled: true (per-repo) → ~/.config/swamp/telemetry.yaml disabled: true (user-global, repo-less runs).
• The spool location (~/.config/swamp/telemetry/, XDG-aware) is not documented anywhere in the manual.

Telemetry stats

• swamp telemetry stats now reads the user-global spool, runs outside a repo, and no longer accepts --repo-dir. Any existing docs or examples referencing telemetry stats --repo-dir are stale.

Migration

• swamp repo upgrade migrates unflushed entries from the legacy repo-local .swamp/telemetry/ spool to the global spool (skipping repos that opted out via telemetryDisabled: true). The old directory is left in place but unused.

The swamp CLI README has already been updated with these changes.