release: t27c 0.5.0 -- the Verified Compute tool chain reaches the registry #7602

Goal

Cut t27c 0.5.0. The crate on crates.io is 0.4.0 (2026-09-21), and since then t27c has gained the Verified Compute tool chain of epic #6655:

• t27c silicon writes signed receipts (R2-1 silicon: every hardware run writes a receipt artifact (R2-1/R2-2) (Closes #7041) #7044, R2-2 seal: built_by -- every new seal names its build (the #7072 prerequisite) #7076, R3-1 verified: t27c signs receipts and run-record judges their level -- R3-1 tool half (Closes #7332) #7363), now with the die's DNA (R3-2 t27c: verify the die's DNA inside a signed receipt -- R3-2 slice 2 tool half (Refs #7452) #7484, t27c silicon: read the die's DNA into the signed receipt -- R3-2 slice 2, reader half (Refs #7452) #7570);
• t27c receipt-key (R3-1);
• t27c run-record, which judges a run's completeness, authentication, die level (feat(verified): t27c run-record reads the receipts and judges one run (R2-4 tool half) #7130, verified: t27c signs receipts and run-record judges their level -- R3-1 tool half (Closes #7332) #7363, t27c: verify the die's DNA inside a signed receipt -- R3-2 slice 2 tool half (Refs #7452) #7484) and independence (R3-3 verified: t27c run-record reports independence across dies, from independence.t27 -- R3-3 tool half (Closes #7600) #7601);
• receipts signed and verified with the .t27 crypto (verified: t27c signs, verifies and hashes with the .t27 crypto; ed25519-dalek and sha2 leave the build (Refs #7332) #7594).

A user who installs t27c from the registry cannot do any of this today.

Boundary

• bootstrap/Cargo.toml version, .zenodo.json version, and the t27c entry in Cargo.lock. These are the files release.yml's VERSION TRUTH gate reads for a t27c-v* tag.
• No code change. ZENODO_DEPOSITION_T27C stays unset, so no DOI is minted, as in 0.4.0.
• The tag t27c-v0.5.0 is pushed only after this PR and the epic's open PRs (verified: t27c signs, verifies and hashes with the .t27 crypto; ed25519-dalek and sha2 leave the build (Refs #7332) #7594, verified: the R3-2 live run is citable -- ternary_link re-sealed with built_by, three signed receipts naming die 050d58218fd9854 (Closes #7452) #7598, verified: t27c run-record reports independence across dies, from independence.t27 -- R3-3 tool half (Closes #7600) #7601) are on master.

User Scenarios & Testing

• Given the tag t27c-v0.5.0 on a master commit carrying this change, release.yml's preflight finds both manifests at 0.5.0, its cargo publish --dry-run passes, and crates.io has no t27c 0.5.0 yet.

Requirements

• FR-1: minor, not patch: new subcommands are additive; the seven backends are untouched.
• FR-2: both manifests are bumped in one commit, so a half-bumped pair fails the PR and not the tag.

Success Criteria

• grep -m1 '^version' bootstrap/Cargo.toml prints version = "0.5.0".
• python3 -c "import json;print(json.load(open('.zenodo.json'))['version'])" prints 0.5.0.
• cargo publish --dry-run --manifest-path bootstrap/Cargo.toml passes on the tagged commit.