cli: output polish batch from the friction walk (#161)

[mbertschler]

Summary

The friction-log walk's S3/S4 output nits, implemented as one landable batch.
These are reporting-only changes — no change to what gets synced, indexed,
or stored; the no-loss/append-only invariants are untouched.

Stacked on #157 (PR #174) — its refused run rows are what the F11d line
rendering now cooperates with. Base retargets to main when #157 merges.

Changes

• F7 — already_correct=N in sync summaries. A no-op-because-in-sync is
  now distinguishable from a no-op-because-empty (transferred=0 alone was
  ambiguous). For rclone bucket pushes and restores it is rclone's
  already-matching count; for peer syncs the handler derives it as
  present-total minus the paths the sync acted on (the Merkle walk never
  sends identical folders to /plan, so it can't be counted from the
  disposition list — added store.CountPresentFilesInVolume).
• F8 — empty-volume warning. A first index of an empty tree warns
  (no files found — new volume, empty directory, or wrong mount?); a wrong
  mount otherwise looks identical to a healthy no-op. index.Report.SawFiles()
  carries the decision so the library stays free of stdout.
• F11a — name the volume in the index summary line (sync already named
  the pair).
• F11b — no rclone.conf updated on a kopia-only sync (kopia never
  touches rclone); the whole rclone preamble is skipped for such a batch.
• F11c — strip kopia's ANSI codes before folding its stderr tail into an
  error, so escape sequences don't leak into the structured log / runs.error.
• F11d — suppress the counter line when a run never reached a terminal
  state (a preflight error before its runs row existed) rather than printing
  status= … run=0. Refused rows minted by runs: every failure and refusal becomes a run row or a standing state #157 still print (they have a
  status and id).
• F18 — label peer direction (→ outbound / ← inbound) in runs and
  the TUI. Only the initiator records runs.shallow, so a set flag marks the
  pushing side — no schema change.
• F19 — runs --failed / runs --changes filters, TUI folding of
  consecutive no-op rows (f toggles), and the runs help no longer claims
  to list only index runs. (See caveat below.)
• F24 — catch-up note. After a burst of new files following a long quiet
  gap, the index summary adds catch-up: N new files after D days of quiet.
• Restore arrow — the restore summary flips to destination → volume,
  matching the byte-flow direction.

Caveat worth a look

runs.file_count conflates transferred with already-correct for bucket
and index runs (it's files considered, not moved), and adding a real "changed"
column would be a schema migration (out of scope while #157 owns v25 / #158
owns v26). So --changes and the TUI fold reliably collapse peer-sync
no-ops (whose file_count is the transferred count) but deliberately keep
bucket/index rows visible rather than risk hiding a run that moved content.
--failed is exact.

Testing

• go build ./..., go vet ./... — clean.
• go test ./... — all packages pass.
• golangci-lint run ./... — 0 issues (rebuilt with the module's go1.26.1
  toolchain; the preinstalled binary refused the newer target version).
• New unit tests: the runs filter predicates, peer-direction arrows,
  catch-up heuristic, index volume-naming + empty warning, stripANSI, and
  the TUI destinationCell/runIsNoOp helpers. rclone-guarded CLI tests
  cover already_correct and the restore arrow (skip where rclone is absent).

Closes #161

🤖 Generated with Claude Code

https://claude.ai/code/session_014Skm2Qm6wWUB7dD4CpPTz7

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Generated by Claude Code

[Copilot]

Pull request overview

This PR polishes CLI/TUI output to address several “friction walk” reporting nits (F7/F8/F11/F18/F19/F24), without changing what data is synced, indexed, or stored.

Changes:

• Add clearer run/sync summaries (e.g., already_correct=N, restore arrow direction, skip rclone preamble for kopia-only batches) and strip kopia ANSI codes from surfaced errors.
• Improve index UX by naming the volume in the summary, warning on first index of an empty tree, and adding an optional catch-up note after long quiet gaps.
• Enhance runs CLI/TUI readability via peer direction arrows, --failed/--changes filters, and TUI folding of consecutive no-op rows.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tui/runs.go	Adds fold markers for consecutive no-op rows and peer direction arrows in the TUI runs table.
tui/runs_polish_test.go	Unit tests for TUI destination arrow rendering and no-op detection.
sync/sync.go	Adds AlreadyCorrect to sync reports and populates it for rclone-based runs.
sync/node.go	Derives AlreadyCorrect for peer syncs using a store count.
sync/kopia.go	Strips ANSI escape sequences from kopia stderr before folding into errors.
sync/kopia_test.go	Tests ANSI stripping behavior.
store/files.go	Adds CountPresentFilesInVolume used for peer-sync “already correct” reporting.
index/index.go	Adds Report.SawFiles() helper to detect empty-tree walks without printing.
cmd/squirrel/sync.go	Skips rclone preamble for kopia-only batches; adds already_correct to summary; suppresses counter line for run-less preflight errors.
cmd/squirrel/sync_test.go	CLI coverage for already_correct and kopia-only “no rclone.conf updated” behavior.
cmd/squirrel/runs.go	Adds --failed/--changes filtering and peer direction arrows in the CLI runs listing.
cmd/squirrel/restore.go	Flips the restore summary arrow to match byte-flow direction.
cmd/squirrel/restore_test.go	Tests restore arrow direction rendering.
cmd/squirrel/polish_test.go	Adds unit tests for runs filters, peer direction arrows, catch-up heuristic, and index advisories.
cmd/squirrel/index.go	Names volumes in index summaries; prints empty-first-index warning and catch-up note.

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