[MDA2AV]

Saving or deploying a version with a lot of resources took the shared server hundreds of megabytes. Every resource was stored inside the version's JSON envelope, text as strings and everything else as base64. Each save and deploy then built and parsed the whole version as one string.

With this PR, a version names each resource by the SHA-256 of what it holds. The lambda's resource store keeps each one once, below {data}/code/{id}/resources/, for every version, feature and preview that ships it.

Measured

The same site was saved, deployed and then served once after a restart, on main and on this branch: HttpArena's, 15 MB in 1,768 files. The server's peak RSS rose by:

	main	this branch
saving + deploying the version	+237 MB, +239 MB	+46 MB, +50 MB
first request after a restart	+111 MB, +141 MB	+37 MB, +55 MB
on disk	23.1 MB	15.3 MB

What changed

• LambdaFile holds content three ways. As text, as the bytes it was read as, or as a reference into the store. It turns one into another only when something asks for it.
  • Archives and pushes keep resources as bytes (FromBytes).
  • Archives and pushes now pass files to new Save and CheckAsync overloads on IMetaService and IFeatureService, rather than serializing them into one text first.
• The two writers fill the store first. LambdaHistory.Append and FeatureService.Save put the resources into the store (LambdaSource.Keep) before writing the envelope that names them. That envelope is "version": 3.
• Reading goes through the store.
  • Going online copies resources out of the store file to file.
  • Archives, exports, published sources and git read them through it (LambdaVersionContent.Files(), FeatureContent.Files(), IStorageService.ReadFiles).
  • Parsed without the store, a stored resource can still be named, counted and compared, but throws when read rather than reading as nothing.
• Envelopes are written with relaxed escaping. The default encoder turned every <, >, & and ' in a page into six characters. An envelope of the second layout, which still carries its resources, is read from its file instead of into a string first.
• Unused resources are collected. A resource that no version, feature or preview names any more is removed together with the version or feature that named it last, once it is an hour old. The hour covers a save in progress, whose resources are kept before the envelope naming them is written. An envelope that can't be read stops the collection.
• The collector conserves memory. System.GC.ConserveMemory is set in the project file, so a spike from one lambda is not held for all of them.
• No frontend change. The API still returns resources inline, as the editor expects.

Compatibility

Nothing stored is rewritten. Versions and features of the second layout are read as they are, resources inside, and use the new layout the next time they are saved. Demos are compared by what their files hold, so the seeder doesn't save them again on every start.

Tests

ResourceStoreTests adds six tests:

• a version names its resources and serves them byte for byte, in pages, zips and the API;
• a resource two versions ship unchanged is kept once;
• a version of the second layout runs, and edits on top of it are saved in the new layout;
• pruning removes what no version names any more;
• deleting a feature removes what only it shipped;
• seeding demos again saves nothing.

Two assertions that expected "version": 2 as today's layout now expect 3. The suite passes, 836 of 836.

Two tests are flaky on main as well, unchanged by this PR:

• TheExportCarriesTheDatabase failed 2 of 4 runs. It scans the machine's temp directory for any recent genhttp-lambda-export-*.db, so it also finds copies from other tests exporting in parallel.
• ABuildTheAgentDeclinedSaysWhyInTheWordsOfTheAgent failed 1 of 4.

Docs

• README: the storage service, how resources are kept, the disk and memory budget, and the GC setting.
• CLAUDE.md: the decisions (how resources are kept, conserving memory) and the layouts.
• The resources.size line of platform_guide.

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