fix(db,ui,docs): an unknown size is absent, not zero, and a share needs a total

[cevheri]

Closes the producer side and the consumer side of one defect: an unknown database size reaching a
reader as a confident zero. Three backlog entries close (D44 in part, D46, U24) and four open in their
place (D50, D51, U25, U26), each measured rather than inferred.

What was wrong

Two providers stated both facts in one object. Trino paired databaseSize: TRINO_UNAVAILABLE_TEXT
with databaseSizeBytes: 0; the search seam paired SEARCH_UNKNOWN_TEXT with sizeBytes ?? 0. The
string said "unavailable" and the number said "zero bytes", from the same input. Both now omit the key,
which is what the optional field is for, and a real zero still reads as zero.

The search seam held the last unconditional activeConnections: 0 (D46). It is absent now, and
getHealth() stops composing a key it has no source for.

The Storage tab divided by a total it did not have. Three figures were affected, not the one the
entry named:

• the remainder bar was drawn FULL over a zero-byte database - 100 - 0 - 0 - and nothing numeric was
  wrong, so no text assertion could see it;
• the Tables and Indexes percentages rendered 0.0% under real megabyte figures, a fabricated
  denominator under an honest numerator;
• the remainder's BYTES rendered -943718400 B when a measured-zero total met per-table reads that
  answered, because getTableStats() is a separate read that does not share the overview's failure.

A share now requires totalSize > 0, which excludes the absent size and the measured zero alike, so one
test covers both. The remainder's bytes are gated on the CONTRADICTION instead, deliberately not on the
share: 0 - 0 - 0 is an honest zero and stays one.

A refused overview lost the engine's sentence in a file that surfaces it for two sibling panels. It
has one now.

The shared formatBytes refused nothing. Measured live: -1, NaN and both infinities all
rendered "NaN undefined", and a petabyte rendered "1 undefined" - a number wearing a missing unit,
which scans as a figure rather than as garbage. Non-magnitudes return "N/A", the ladder gains PB and
EB, and the index is CLAMPED, which makes indexing past the array unreachable rather than moving the
boundary up two rungs.

Three claims this repo made about itself, corrected

The backlog entry, docs/providers/mongodb.md and a mongodb.ts comment all said the negative
remainder renders NaN undefined. It does not. StorageTab defines its OWN local byte formatter and
never imports the shared one, so the cell renders -1536 B. A review lane had reported exactly that in
the previous round and was overruled by a measurement of the wrong function.

The search docs asserted that TableStats "has no way to say unknown - both fields are required
numbers". Measured against types.ts: rowCount, totalSize and totalSizeBytes are required;
tableSize, tableSizeBytes, indexSize and indexSizeBytes are optional, and their own docblock
argues for absence. Corrected here; the code half is D50.

A new comment claimed the search provider held "the last zero". It held the last unconditional literal
one. Four providers still reach a zero by a longer route, which is D51.

New entries, all measured

• D50 - the search seam zeroes two OPTIONAL TableStats size fields for a closed index. Not fixed
  here because omitting them takes the Data figure away from every open index in the cluster
  (tables.every(...)), which is a visible panel change and wants its own decision.
• D51 - Trino, Druid, ClickHouse and Couchbase each degrade a refused monitoring read to no rows and
  then map the absent row to 0. ClickHouse's does it to six fields at once, so one refused read
  publishes a fully-zeroed overview that reads as measured.
• U25 - formatBytes exists three times; the two component-local copies have no guard and render
  -1 B, NaN B, Infinity GB.
• U26 - the admin fleet total re-parses formatted strings and has no tb branch, so a 1 TB database
  contributes 1 byte. The real defect is that FleetHealthItem carries no numeric channel at all.

Verification

• Six local gates green; coverage 100%.
• Every lane's work was reviewed adversarially, and four review findings were verified before adoption -
  one of them enlarged (Trino belonged in D51 and the reviewer had not measured it), one narrowed.
• Non-vacuity proven by mutation for each new guard: reverting remainderKnown's non-negative check,
  the Quick Stats gate, and the three *Unavailable guards' === undefined half each turns the suite
  RED. That last one is a guard shape that had existed for two rounds with nothing pinning it.
• A second test file the triad invariant does not name - tests/unit/db/trino/introspect.test.ts -
  asserted the old 0. Only a test run found it.

[sonarqubecloud]

Quality Gate passed

Issues
7 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud