fix(loop): run applyCompression over the unpruned view

[ranxianglei]

Feature branch (split out of #194 per review: features and releases stay separate).

Problem

The streaming compress path fed applyCompression a view that had neither
the raw messages nor the rendered summaries:

• server.ts runCompressLoop ctx: messages: prepared.processedMessages.length > 0 ? prepared.processedMessages : prepared.originalMessages
• processedMessages = stripKernelSummaries(turn.messages) filters every acp_summary_* id
• → loop/core.ts executeProxyTool → stream.ts applyCompression({ messages: ctx.messages })

With kernel ≥0.0.37 (billion-context-pi#195 fix), block anchors resolve via the
rendered summary or surviving raws — a view containing neither can resolve
nothing, so compression of any pruned region fails in streaming mode.

Fix

Split the two purposes of LoopCtx.messages:

• new optional compressMessages?: CoreMessage[] on RewriteCtx (src/stream.ts) and LoopCtx (src/loop/core.ts)
• applyRanges uses ctx.compressMessages ?? ctx.messages (src/stream.ts)
• server.ts runCompressLoop sets compressMessages: prepared.originalMessages (full unpruned log — anchors always resolvable)
• wire rebuilds / decompress / status keep using the pruned view (unchanged behavior)

Non-streaming paths already used originalMessages — no change for them.

Validation

• typecheck clean; 512/512 tests; build OK (on pinned acp-kernel 0.0.36)
• e2e grow-and-compress passes with kernel 0.0.41 overlay (upstream body stays bounded)

Ships in the next release together with the acp-kernel bump (≥0.0.40 for
billion-context-pi#195/#199 fixes).