fix(covgate,covratchet): progress is the single canonical table

[ben-miru]

Summary

Follow-up to #32. The live progress block and the alphabetical recap table carried the exact same per-package rows, doubling output without adding information — the user reported "the spacing is off" and then "the first and second table give exact same information, please only show first table".

Now, when --parallelism=0:

• The streamed progress block (with the new leading COUNT column under [N/total]) is the single canonical table.
• Per-package rows print only once, in completion order.
• The second STATUS header and reprinted rows are removed.
• FAIL detail (multi-line raw test output for testErr cases) still prints after the stream — that's not duplicated data.
• --exclude SKIPPED rows still print, indented under the COUNT column so they align with the progress table's STATUS column.

Non-progress mode (--parallelism>0) is unchanged: a single alphabetical table, no progress stream.

Before (current main)

Running 27 packages with parallelism=22; progress will appear as packages finish:
STATUS   COVERAGE  REQUIRED      TIME  PACKAGE
-------  --------  --------  --------  -------
[8/27] PASS  internal/pkg/openapi/server  0.8s            <- columns don't align
...
PASS         0.0%      0.0%      0.8s  internal/pkg/openapi/server   <- same data again
...

After

Running 27 packages with parallelism=22; progress:
COUNT    STATUS   COVERAGE  REQUIRED      TIME  PACKAGE
-------  -------  --------  --------  --------  -------
[ 8/27]  PASS         0.0%      0.0%      0.8s  internal/pkg/openapi/server
[21/27]  PASS         0.0%      0.0%      1.1s  internal/pkg/server/response
...
[27/27]  PASS         0.3s  ...

Total time: 5.4s
All packages meet minimum coverage requirement

With --exclude, SKIPPED rows appear indented under the COUNT column:

[ 1/10]  PASS        62.7%     62.3%      0.3s  internal/commands
[10/10]  PASS         0.0%      0.0%      0.3s  internal/testutil
         SKIPPED       ---       ---       ---  internal/services/lint
         SKIPPED       ---       ---       ---  internal/services/lint/linter
         ...

Total time: 0.3s
All packages meet minimum coverage requirement

Notes

• progressColWidth(total) scales the COUNT column with package count: [ 8/27] is 7 chars for 27 packages, [ 88/100] is 9 for 100.
• Extracted writeRunHeader in both packages to keep run() under the 50-line funclen limit after the bracketing/header logic was added.
• restOfOutput is the dual of firstLine — used in progress mode to print only the trailing FAIL detail of checkResult.output, not the row that was already streamed.
• Test assertions updated: STATUS header appears exactly once (progress IS the table); a COUNT header is present in progress mode and absent otherwise; progress lines must carry full row data.

Test plan

• go test ./internal/services/covgate/... ./internal/services/covratchet/... passes
• ./scripts/preflight.sh ends with === All checks passed ===
• Smoke-tested go run ./cmd/miru covgate --packages="./internal/..." --src-prefix=internal --parallelism=0 — single table, no duplicate
• Smoke-tested same with --exclude=./internal/services/lint/... — SKIPPED rows render indented under COUNT

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