feat(inbox): add --include-self flag to capture self-authored @mentions

[aliir74]

Summary

• clickup inbox silently filters out comments where the user @mentioned themselves, which hides a deliberate "remind myself later" workflow on teammates' tasks.
• Adds an opt-in --include-self flag that, when set, includes self-authored mentions alongside the normal incoming ones.
• Default behavior is unchanged: without the flag, the existing filter still applies. Zero impact on existing users.

Implementation

• Filter at pkg/cmd/inbox/inbox.go rewritten as if containsMention(...) && (opts.includeSelf || !isSelf).
• Cache round-trip: inboxCache gets a new include_self field. If the flag setting differs from the cached run's setting, the cache is treated as stale and a cold rescan kicks in. This avoids the case where a previous default-off run cached "no mentions" for tasks that actually have self-mentions.
• Test coverage:
  • TestNewCmdInbox_Defaults extended to assert the new flag exists and defaults to false.
  • TestInboxCache_FlagMismatchInvalidates covers the JSON round-trip of the new cache field.

Test plan

• go test ./pkg/cmd/inbox/... → 70 passed (69 prior + 1 new)

• go test ./... → 751 passed across 45 packages

• Manual: clickup inbox --json --days 7 --include-self --no-cache against a real workspace recovers self-authored @mentions that the default run omits

• Manual: toggling --include-self between consecutive runs triggers a cache rescan as expected

• I have assessed security implications of this change

• I have tested this change (automating where feasible)

• I have updated the documentation (where applicable)

[isaacrowntree]

Clean, well-scoped change. A few checks I ran:

Correctness

• Filter reduces to the old condition when includeSelf=false: containsMention && (false || !isSelf) ≡ containsMention && !isSelf. ✓
• Cache invalidation on flag mismatch is correct — mentionsByTask is filter-dependent, so toggling must force a rescan.
• JSON round-trip is safe: existing cache files without include_self deserialize to IncludeSelf: false, matching default behavior. No migration needed.

Minor notes (not blockers)

• Description mentions (r.task.Description, inbox.go:246) don't have a self-author concept and are always included regardless of the flag. Pre-existing behavior, out of scope here — flagging in case you want a follow-up.
• Each toggle of --include-self triggers a full cold rescan. Acknowledged in the PR description and the right trade-off.

LGTM.