Record post-660 investigate productivity measurement

[ericlitman]

Problem

PR #777 restored the investigate-productivity CLI, but the required post-SYMPH-660 production measurement still existed only in host-local operational artifacts. This change makes the measured distribution, fuse audit, and dependent-ticket decision durable in the repository.

Scope

• Records three post-SYMPH-660 first-pass investigate units and one post-workpad retry from pro14.
• Embeds the exact retained token, cache, weighted-envelope, window-share, turn, and outcome values plus source hashes.
• Audits the observed distribution against the active iteration, weighted-token, legacy-dollar, and window-share envelope values.
• Records the SYMPH-661 no-go/cancel decision and the measured 300k / 600k / 1.2M seed for SYMPH-1157.

This PR changes one documentation file. It does not change runtime code, tests, configuration, specifications, report semantics, hard-stop policy, or right-sizing behavior.

Evidence

• Production host: pro14
• Measured merge: da06fd2217635d221afcff4e0e3d3e312f13d8c6 (PR Restore investigate productivity report CLI #777)
• Enriched measurement SHA-256: b3dc7d9e946c78d7511cbb35676b4121b8c901968e3352b10009b02f4c2cb2ce
• Controller generation: 8ccf119c03f49ef3fd98b0ed24c17b11d8c38f44

Validation

Controller-authoritative validation passed on the complete corrected artifact:

• pnpm install --frozen-lockfile
• pnpm build
• pnpm docs:check
• pnpm lint

Linear: SYMPH-1155

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[ericlitman]

Governed review evidence — fixed head f209b32b

• Review tier: crabbox-council via the installed controller generation 8ccf119c.
• Round 1 crabbox-council-20260715T194513.794Z: all four jobs completed; three finder lanes returned PASS with zero findings.
• Round 2 crabbox-council-20260715T195018.252Z: unchanged-head full-diff review. The nonblocking 20%/10% wording drift is tracked in SYMPH-1166. Opus-extra downgraded the sole contested host-local-path P2 to Track because the committed values and hashes remain independently verifiable; that provenance follow-up is SYMPH-1167.
• Convergence: two clean, cross-examined rounds over f209b32b; zero surviving P1/P2 findings.
• Validation: controller install/build/docs-check/lint green; local typecheck green; every GitHub test, architecture, diff-coverage, security, and CodeQL check green on f209b32b.
• A local full-suite timing assertion flaked once outside the changed surface, then passed 3/3 focused runs and 2/2 complete runtime-host-file runs. The same-head GitHub suite is green; the flake is tracked in SYMPH-1168.
• Auto-merge gate: can_merge: true; base da06fd22 current, CLEAN/MERGEABLE, no conflicts.

The reviewed head stayed fixed throughout both rounds.