feat: add Solana fixed-yield brief plugin

[sheawinkler]

What

Adds solana-fixed-yield-brief, a T0/read-only wasm32-wasip2 tool plugin
that:

• fetches fixed official Exponent vault, SY-token, and quote endpoints;
• filters to coherent SOL-normalized Principal Token markets;
• compares bounded live BASE_TO_PT quotes with a non-weakenable 5.50%
  staking hurdle and explicit cost allowance;
• ranks a bounded 3/6/8 quote fan-out by term excess and defaults to one compact
  result;
• returns exact base/PT identities, coverage, unit assumptions, the unquoted
  base-token leg, and non-approval risk labels.

The plugin accepts no wallet, key, transaction, config, filesystem access, or
caller-controlled URL. Its only manifest permission is http_client.

Why

An APY headline is not an executable wallet return. Exponent's BASE_TO_PT
amount is normalized-SOL accounting notional; an LST-backed market can require
its underlying base token rather than native SOL. The plugin therefore exposes
that acquisition/redemption gap and never presents a quote as a funded trade or
execution approval.

Safety and integrity

• fixed HTTPS origins; 10-second connect timeout; bounded bodies, catalogs,
  venue lists, routes, quote fan-out, and output;
• strict typed parsing, 32-byte Base58 Solana pubkeys, exact UTC maturity
  parsing, duplicate-identity rejection, and pre/post-I/O clock checks;
• catalog price/APY and live quote/APY reconciliation;
• route input/output/fee/percentage/type/address reconciliation;
• explicit normalized-SOL/base/PT unit types and a narrowly admitted
  one-for-one atomic-scale assumption;
• missing quote-critical fields, malformed data, zero coherent quotes, and
  partial coverage fail closed or remain explicitly UNPROVEN;
• remote names/tickers are never rendered;
• hostile action/recipient/amount/privateKey tool fields are
  rejected before clock or network access;
• structured success diagnostics use log-record; no stdout from the
  component.

Authoritative local verification

Committed snapshot:
af5c036c32d650509832e7c76a7a5f7a9c9c4ed4

cargo fmt -- --check                                      PASS
cargo test --locked                                       PASS (28 passed)
cargo clippy --locked --all-targets -- -D warnings        PASS
cargo build --locked --target wasm32-wasip2 --release     PASS
cargo clippy --locked --target wasm32-wasip2 -- -D warnings
                                                            PASS
cargo audit --file Cargo.lock --deny warnings              PASS (76 dependencies)
python3 -m unittest discover -s tools/tests -p 'test_*.py'
                                                            PASS (17 passed)
python3 -m unittest discover -s tools/ci/tests -p 'test_*.py'
                                                            PASS (36 passed)

The repository's strict clean-snapshot validator independently passed tests,
native Clippy, WASI Clippy, release build, source-mutation detection, and
component staging:

source_head: af5c036c32d650509832e7c76a7a5f7a9c9c4ed4
tests: 28 passed / 0 failed / 0 ignored
host clippy: 0
wasm clippy: 0
release build: 0
artifact: 423310 bytes
artifact sha256: 3e89d09e2028b8f7f9b49ab95fd390db264f4874d28a8770cfd0dd59685fee41
source mutation: none

Real ZeroClaw host execution

A fresh release harness built against ZeroClaw commit
f0b92f1516ec86aeb89ab2d8f25b837e14885aae loaded the final component through
the actual PluginHost/Wasmtime bridge. The four relevant WIT files were
byte-identical.

• harness SHA-256:
  bf051d8265ca4011815cedba98c699bf523e362e5957ec4b0d838e31dce1e803
• discovered exactly solana-fixed-yield-brief v0.1.0 with
  permissions=[HttpClient];
• completed a live 0.9 normalized-SOL call with success=true, 3/3 attempted
  coherent quotes across 4 eligible markets, one best candidate, and explicit
  partial-coverage warning;
• live result: 562 bytes, 221 o200k_base tokens, 222 cl100k_base
  tokens;
• returned success=false for the hostile fund-move/private-key argument
  set.

The component transport exposes a connect timeout but not a total/read
deadline; the verified host supplies a 30-second outer cancellation boundary.

Full reproducible evidence and the exact observed output are in
DEMO.md.

Human-only bounty artifact

The real Telegram/Discord, no-slide video and Superteam submission remain
human-produced artifacts. The README and demo record provide the exact
invocation and hostile-message sequence; this PR does not misrepresent the local
host execution as channel proof.