test: add a coverage floor, and cover the server and upgrade paths

[titouanmathis]

The floor

test:ci now fails when coverage drops below a threshold set just under the current numbers — a regression fails, an improvement doesn't.

Verified it actually bites, rather than passing silently:

ERROR: Coverage for statements (76.24%) does not meet global threshold (99%)
exit code: 1

This is the gate for the problem behind several fixes this cycle: loadProjectList and routePath each had no tests and each hid a bug for nine releases.

	statements	branches	functions	lines
agent floor	75	70	70	75
agent actual	76.24	71.37	70.66	76.87
CLI floor	95	92	100	95
CLI actual	97.02	93.06	100	97

Reaching a floor worth having

server.ts: 5.8% → 66.7%. The handlers take a ServerDeps seam holding the project index, the per-project configs and the side effects, so a test drives them with a known world and records what they did — no socket, no database, no DDEV install.

The cases are about decisions, not plumbing:

• a project's own auth_policy overrides the global one, while credentials stay server-wide
• a second request during a start does not queue another ddev start
• a failed start records stopped rather than leaving the project wedged on starting
• /__auth__?s=term reaches the auth handler — the query-string routing bug from 0.1.33, now pinned down

setup/upgrade.ts: 18.9% → 66.7%. runUpgrade takes an UpgradeIo, which is what makes the re-exec path testable without replacing the process. The two guards worth covering are both loops:

• no re-exec when npm served a stale cache and left the old version in place
• no second re-exec once one has happened

Plus: an unreachable registry must not stop migrations that are already due.

Notes

Agent overall 66.8% → 76.2%. 474 tests, no mocks — the new fakes follow the injection convention from #51.

The floors are deliberately a ratchet, not a target. server.ts still has uncovered startup plumbing and upgrade.ts its process-level helpers; raise the numbers as those get covered.

[codecov]

Codecov Report

❌ Patch coverage is 84.61538% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.12%. Comparing base (46241f0) to head (e71bb19).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/trafic-agent/src/server.ts	84.00%	4 Missing ⚠️
packages/trafic-agent/src/setup/upgrade.ts	85.71%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #52      +/-   ##
==========================================
+ Coverage   75.42%   82.12%   +6.70%     
==========================================
  Files          35       35              
  Lines        1461     1466       +5     
  Branches      373      374       +1     
==========================================
+ Hits         1102     1204     +102     
+ Misses        292      219      -73     
+ Partials       67       43      -24     

Flag	Coverage Δ
integration	65.74% <ø> (ø)
unit	81.92% <84.61%> (+6.70%)	⬆️

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