per-server annotation overrides for misbehaving upstreams

[DScoNOIZ]

Hi, ran into this with a couple of old mcp servers, browseros in my case. They dont send any annotations at all, so all their tools fall into destructive tier by default. Readonly agents cant even see plain readers like navigate or snapshot, even though theres nothing dangerous in them. Patching every upstream by hand is obviously not an option, so I made operator side overrides.

How it works, theres a new optional map annotation_overrides in the server config. Key is the tool name or a star for all of them at once, value is annotations. Merges per hint on top of what the server sent, priority is straightforward, exact then wildcard then upstream. Whatever is not set is inherited. You can delete with null by key, same as everywhere else in the config. Only admin can change it, both rest and mcp. No restart needed, applies right away on the next get. Written to audit as config_change. Left the tool approval hash alone, its got no business there.

On the ui side I put a card into the server configuration right after trust mode. Theres a compact table plus a mark safe button per tool, it just presets readonly true destructive false and thats it. It never touches openWorldHint by itself, thats manual only if youre really sure. Left the selects three state inherit true false, cause a toggle just cant express inherit.

Compat wise all quiet. Field is omitempty everywhere, old configs load like they used to, without overrides behavior is exactly like before. Covered merge priority validation and admin only with tests. Docs added in config-file and upstream-servers, swagger regenerated.

Tested live on browseros, 24 tools there and 5 with no annotations at all. Readonly token used to see zero browseros tools, after the override navigate is found and called through the read door. Deleted the override and everything flipped right back. If something doesnt fit or needs splitting up, let me know, will rework.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 33.70647% with 533 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/httpapi/server.go	21.32%	154 Missing and 12 partials ⚠️
internal/server/server.go	28.34%	80 Missing and 11 partials ⚠️
internal/config/merge.go	36.80%	60 Missing and 19 partials ⚠️
internal/server/mcp.go	36.60%	62 Missing and 9 partials ⚠️
internal/config/annotation_overrides.go	31.31%	62 Missing and 6 partials ⚠️
internal/config/config.go	51.28%	14 Missing and 5 partials ⚠️
internal/audit/line.go	0.00%	13 Missing ⚠️
internal/server/mcp_trust_mode.go	0.00%	11 Missing ⚠️
internal/server/preflight_glue.go	66.66%	5 Missing and 1 partial ⚠️
internal/server/mcp_direct_catalog.go	75.00%	1 Missing and 2 partials ⚠️
... and 3 more

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